wip new type system and refactoring

- Result -> RTNode
- Stream -> Result
- ValueStream -> SigStream
- EventStream -> EvtStream

29 files changed, 845 insertions, 561 deletions

diff --git a/alv/ast.moon b/alv/ast.moon
index 7090869..cff8947 100644
--- a/alv/ast.moon
+++ b/alv/ast.moon
@@ -1,7 +1,7 @@
 ----
 -- AST Node Interface.
 --
--- implemented by `ValueStream` and `Cell`.
+-- implemented by `Constant` and `Cell`.
 --
 -- @classmod AST
 
diff --git a/alv/base/init.moon b/alv/base/init.moon
index c37d85c..71e9cea 100644
--- a/alv/base/init.moon
+++ b/alv/base/init.moon
@@ -11,10 +11,11 @@
 -- @see Input
 -- @see base.match.val
 -- @see base.match.evt
--- @see ValueStream
--- @see EventStream
+-- @see Constant
+-- @see SigStream
+-- @see EvtStream
 -- @see IOStream
--- @see Result
+-- @see RTNode
 -- @see Error
 
 import Op from require 'alv.base.op'
@@ -22,8 +23,8 @@ import Builtin from require 'alv.base.builtin'
 import FnDef from require 'alv.base.fndef'
 import Input from require 'alv.base.input'
 import val, evt from require 'alv.base.match'
-import ValueStream, EventStream, IOStream from require 'alv.stream'
-import Result from require 'alv.result'
+import Constant, SigStream, EvtStream, IOStream from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
 
 {
@@ -34,6 +35,6 @@ import Error from require 'alv.error'
   :val, :evt
 
   -- redundant exports, to keep anything an extension might need in one import
-  :ValueStream, :EventStream, :IOStream
-  :Result, :Error
+  :Constant, :SigStream, :EvtStream, :IOStream
+  :RTNode, :Error
 }
diff --git a/alv/base/input.moon b/alv/base/input.moon
index fe01f88..dea91c9 100644
--- a/alv/base/input.moon
+++ b/alv/base/input.moon
@@ -2,8 +2,8 @@
 -- Update scheduling policy for `Op` arguments.
 --
 -- @classmod Input
-import ValueStream, EventStream, IOStream from require 'alv.stream'
-import Result from require 'alv.result'
+import Constant, SigStream, EvtStream, IOStream from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 
 inherits = (klass, frm) ->
   assert klass, "cant find the ancestor of nil"
@@ -53,7 +53,7 @@ class Input
   --
   -- must return a boolean indicating whether `Op`s that refer to this instance
   -- should be notified (via `Op:tick`). If not overwritten, delegates to
-  -- `stream`:@{ValueStream:dirty|dirty}.
+  -- `stream`:@{SigStream:dirty|dirty}.
   --
   -- @treturn bool whether processing is necessary
   dirty: => @stream\dirty!
@@ -77,7 +77,7 @@ class Input
 
   --- the current value
   --
-  -- @tfield ValueStream stream
+  -- @tfield SigStream stream
 
 --- members
 -- @section members
@@ -98,9 +98,9 @@ class Input
   -- Never marked dirty. Use this for input streams that are only read when
   -- another `Input` is dirty.
   --
-  -- @tparam Stream|Result value
+  -- @tparam Stream|RTNode value
   @cold: (value) ->
-    if value.__class == Result
+    if value.__class == RTNode
       value = assert value.value, "Input from result without value!"
     ColdInput value
 
@@ -108,15 +108,15 @@ class Input
   --
   -- Behaviour depends on what kind of `Stream` `value` is:
   --
-  -- - `ValueStream`: Marked dirty only if old and new `ValueStream` differ.
-  -- - `EventStream` and `IOStream`: Marked dirty only if the current
-  --   `EventStream` is dirty.
+  -- - `SigStream`: Marked dirty only if old and new `SigStream` differ.
+  -- - `EvtStream` and `IOStream`: Marked dirty only if the current
+  --   `EvtStream` is dirty.
   --
   -- This is the most common `Input` strategy.
   --
-  -- @tparam Stream|Result value
+  -- @tparam Stream|RTNode value
   @hot: (value) ->
-    if value.__class == Result
+    if value.__class == RTNode
       value = assert value.value, "Input from result without value!"
 
     InputType = match_parent value, mapping
@@ -137,8 +137,9 @@ class IOInput extends Input
   io: true
 
 mapping = {
-  [ValueStream]: ValueInput
-  [EventStream]: Input
+  [Constant]: ColdInput
+  [SigStream]: ValueInput
+  [EvtStream]: Input
   [IOStream]: IOInput
 }
 
diff --git a/alv/base/match.moon b/alv/base/match.moon
index 62075c0..819b0b4 100644
--- a/alv/base/match.moon
+++ b/alv/base/match.moon
@@ -2,7 +2,7 @@
 --- Pattern capturing for Op argument parsing.
 --
 -- There is only one basic buildings block for assembling patterns:
--- `Type`. It can match `ValueStream`s and `EventStream`s depending on its
+-- `Type`. It can match `SigStream`s and `EvtStream`s depending on its
 -- metatype argument and can take an optional type name to match as an argument.
 --
 -- In addition to this primitive, the following modifiers are available:
@@ -21,12 +21,12 @@
 -- - `-pat`: Shorthand for `Optional(pat)`
 --
 -- To perform the actual matching, call the `:match` method on a pattern and
--- pass a sequence of `Result`s. The method will either return the captured
--- `Result`s (or a table structuring them)
+-- pass a sequence of `RTNode`s. The method will either return the captured
+-- `RTNode`s (or a table structuring them)
 --
 -- Any ambiguous pattern can be set to 'recall mode' by invoking it.
--- Recalling patterns will memorize the first Result they match, and
--- only match further Results of the same type. For example
+-- Recalling patterns will memorize the first RTNode they match, and
+-- only match further RTNodes of the same type. For example
 --
 --     arg = (val.num / val.str)!
 --     pattern = arg + arg
@@ -45,14 +45,11 @@
 --
 -- @module base.match
 import Error from require 'alv.error'
-import ValueStream, EventStream from require 'alv.stream'
+import Primitive from require 'alv.types'
 
 local Repeat, Sequence, Choice, Optional
 
-typestr = (result) ->
-  str = result\type!
-  str ..= '!' if result\metatype! == 'event'
-  str
+typestr = (result) -> tostring result.value
 
 class Pattern
   match: (seq) =>
@@ -107,13 +104,17 @@ class Type extends Pattern
   capture: (seq, i) =>
     return unless seq[i]
     type, mt = seq[i]\type!, seq[i]\metatype!
-    return unless @metatype == mt
+    if @metatype == 'event'
+      return unless mt == '!'
+    else
+      return if mt == '!'
+
     match = if @type then type == @type else @remember type
     if match
       1, seq[i]
 
   __tostring: =>
-    str = @type or @metatype
+    str = tostring @type or @metatype
     str ..= '!' if @metatype == 'event'
     str
 
@@ -272,7 +273,7 @@ class Optional extends Pattern
 -- @table val
 val = setmetatable {}, {
   __index: (key) =>
-    with v = Type 'value', key
+    with v = Type 'value', Primitive key
       @[key] = v
 
   __call: (...) => Type 'value', ...
@@ -290,7 +291,7 @@ val = setmetatable {}, {
 -- @table evt
 evt = setmetatable {}, {
   __index: (key) =>
-    with v = Type 'event', key
+    with v = Type 'event', Primitive key
       @[key] = v
 
   __call: (...) => Type 'event', ...
diff --git a/alv/builtin.moon b/alv/builtin.moon
index c80e483..767d8e1 100644
--- a/alv/builtin.moon
+++ b/alv/builtin.moon
@@ -6,16 +6,17 @@
 --
 -- @module builtin
 import Builtin, Op, FnDef, Input, val, evt from require 'alv.base'
-import ValueStream, LiteralValue from require 'alv.stream.value'
+import Constant from require 'alv.result'
 import Error from require 'alv.error'
-import Result from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 import Cell from require 'alv.cell'
 import Scope from require 'alv.scope'
 import Tag from require 'alv.tag'
 import op_invoke from require 'alv.invoke'
+import Primitive from require 'alv.types'
 lfs = require 'lfs'
 
-doc = ValueStream.meta
+doc = Constant.meta
   meta:
     name: 'doc'
     summary: "Print documentation in console."
@@ -36,11 +37,11 @@ doc = ValueStream.meta
       assert #tail == 1, "'doc' takes exactly one parameter"
 
       result = L\push tail[1]\eval, scope
-      with Result children: { def }
+      with RTNode children: { def }
         meta = result.value.meta
         L\print "(doc #{tail[1]}):\n#{format_meta meta}\n"
 
-def = ValueStream.meta
+def = Constant.meta
   meta:
     name: 'def'
     summary: "Declare symbols in current scope."
@@ -63,9 +64,9 @@ Define the symbols `sym1`, `sym2`, … to resolve to the values of `val-expr1`,
           with val_expr\eval scope
             scope\set name, \make_ref!
 
-      Result :children
+      RTNode :children
 
-use = ValueStream.meta
+use = Constant.meta
   meta:
     name: 'use'
     summary: "Merge scopes into current scope."
@@ -82,9 +83,9 @@ All arguments have to be evaltime constant."
         value = result\const!
         scope\use value\unwrap 'scope', "'use' only works on scopes"
 
-      Result!
+      RTNode!
 
-require_ = ValueStream.meta
+require_ = Constant.meta
   meta:
     name: 'require'
     summary: "Load a module."
@@ -102,7 +103,7 @@ require_ = ValueStream.meta
       L\trace @, "loading module #{name}"
       COPILOT\require name
 
-import_ = ValueStream.meta
+import_ = Constant.meta
   meta:
     name: 'import'
     summary: "Require and define modules."
@@ -120,9 +121,9 @@ current scope."
         name = child\unwrap 'sym'
         with COPILOT\require name
           scope\set name, \make_ref!
-      Result :children
+      RTNode :children
 
-import_star = ValueStream.meta
+import_star = Constant.meta
   meta:
     name: 'import*'
     summary: "Require and use modules."
@@ -138,9 +139,9 @@ Requires modules `sym1`, `sym2`, … and merges them into the current scope."
       children = for i, child in ipairs tail
         with COPILOT\require child\unwrap 'sym'
           scope\use .value\unwrap 'scope'
-      Result :children
+      RTNode :children
 
-export_ = ValueStream.meta
+export_ = Constant.meta
   meta:
     name: 'export'
     summary: "Evaluate definitions in a new scope and return it."
@@ -152,9 +153,9 @@ Evaluate `expr1`, `expr2`, … in a new Scope and return scope."
     eval: (scope, tail) =>
       new_scope = Scope scope
       children = [expr\eval new_scope for expr in *tail]
-      Result :children, value: ValueStream.wrap new_scope
+      RTNode :children, value: Constant.wrap new_scope
 
-export_star = ValueStream.meta
+export_star = Constant.meta
   meta:
     name: 'export*'
     summary: "Export specific symbol definitions as a module/scope."
@@ -179,9 +180,9 @@ Copies the containing scope if no symbols are given."
           with result = scope\get name
             new_scope\set name, result
 
-      Result :children, value: ValueStream.wrap new_scope
+      RTNode :children, value: Constant.wrap new_scope
 
-fn = ValueStream.meta
+fn = Constant.meta
   meta:
     name: 'fn'
     summary: "Declare a function."
@@ -201,13 +202,13 @@ function is invoked."
         assert param.type == 'sym', "function parameter declaration has to be a symbol"
         param
 
-      Result value: with ValueStream.wrap FnDef param_symbols, body, scope
+      RTNode value: with Constant.wrap FnDef param_symbols, body, scope
         .meta = {
           summary: "(user defined function)"
           examples: { "(??? #{table.concat [p! for p in *param_symbols], ' '})" }
         }
 
-defn = ValueStream.meta
+defn = Constant.meta
   meta:
     name: 'defn'
     summary: "Define a function."
@@ -229,16 +230,16 @@ function is invoked."
         assert param.type == 'sym', "function parameter declaration has to be a symbol"
         param
 
-      value = with ValueStream.wrap FnDef param_symbols, body, scope
+      value = with Constant.wrap FnDef param_symbols, body, scope
         .meta =
           :name
           summary: "(user defined function)"
           examples: { "(#{name} #{table.concat [p! for p in *param_symbols], ' '})" }
 
-      scope\set name, Result :value
-      Result!
+      scope\set name, RTNode :value
+      RTNode!
 
-do_expr = ValueStream.meta
+do_expr = Constant.meta
   meta:
     name: 'do'
     summary: "Evaluate multiple expressions in a new scope."
@@ -250,9 +251,9 @@ Evaluate `expr1`, `expr2`, … and return the value of the last expression."
     eval: (scope, tail) =>
       scope = Scope scope
       children = [expr\eval scope for expr in *tail]
-      Result :children, value: children[#children].value
+      RTNode :children, value: children[#children].value
 
-if_ = ValueStream.meta
+if_ = Constant.meta
   meta:
     name: 'if'
     summary: "Make an evaltime const choice."
@@ -277,7 +278,7 @@ to `then-expr`, otherwise it is equivalent to `else-xpr` if given, or nil otherw
       elseif xelse
         xelse\eval scope
 
-trace_ = ValueStream.meta
+trace_ = Constant.meta
   meta:
     name: 'trace!'
     summary: "Trace an expression's value at evaltime."
@@ -291,7 +292,7 @@ trace_ = ValueStream.meta
       with result = L\push tail[1]\eval, scope
         L\print "trace! #{tail[1]\stringify!}: #{result.value}"
 
-trace = ValueStream.meta
+trace = Constant.meta
   meta:
     name: 'trace'
     summary: "Trace an expression's values at runtime."
@@ -313,13 +314,13 @@ trace = ValueStream.meta
 
       tag = @tag\clone Tag.parse '-1'
       inner = Cell tag, {
-        LiteralValue 'opdef', traceOp, 'trace'
-        ValueStream.str tostring tail[1]
+        Constant.literal (Primitive 'opdef'), traceOp, 'trace'
+        Constant.str tostring tail[1]
         tail[1]
       }
       inner\eval scope
 
-print = ValueStream.meta
+print = Constant.meta
   meta:
     name: 'print'
     summary: "Print string values."
@@ -348,23 +349,23 @@ Scope.from_table {
   export: export_
   'export*': export_star
 
-  true: ValueStream.meta
+  true: Constant.meta
     meta:
       name: 'true'
       summary: "The boolean constant `true`."
-    value: ValueStream.bool true
+    value: Constant.bool true
 
-  false: ValueStream.meta
+  false: Constant.meta
     meta:
       name: 'false'
       summary: "The boolean constant `false`."
-    value: ValueStream.bool false
+    value: Constant.bool false
 
-  bang: ValueStream.meta
+  bang: Constant.meta
     meta:
       name: 'bang'
       summary: "A `bang` value-constant."
-    value: ValueStream 'bang', true
+    value: Constant 'bang', true
 
   :fn, :defn
   'do': do_expr
diff --git a/alv/cell.moon b/alv/cell.moon
index 6d5e207..2e00195 100644
--- a/alv/cell.moon
+++ b/alv/cell.moon
@@ -5,9 +5,10 @@
 -- nodes), a `Tag`, and optionally the internal whitespace as parsed.
 --
 -- @classmod Cell
-import ValueStream from require 'alv.stream'
+import Constant from require 'alv.result'
 import Error from require 'alv.error'
 import op_invoke, fn_invoke from require 'alv.invoke'
+import Primitive from require 'alv.types'
 import Tag from require 'alv.tag'
 
 local RootCell
@@ -73,11 +74,11 @@ class Cell
     head = assert @head!, Error 'syntax', "cannot evaluate empty expr"
     head = (head\eval scope)\const!
     Builtin = switch head.type
-      when 'opdef'
+      when (Primitive 'opdef')
         op_invoke
-      when 'fndef'
+      when (Primitive 'fndef')
         fn_invoke
-      when 'builtin'
+      when (Primitive 'builtin')
         head\unwrap!
       else
         error Error 'type', "#{head} is not an opdef, fndef or builtin"
@@ -157,7 +158,7 @@ class Cell
 
 -- @type RootCell
 class RootCell extends Cell
-  head: => ValueStream.sym 'do'
+  head: => Constant.sym 'do'
   tail: => @children
 
   clone: (parent) =>
diff --git a/alv/copilot.moon b/alv/copilot.moon
index 7ef2134..d9b674f 100644
--- a/alv/copilot.moon
+++ b/alv/copilot.moon
@@ -6,8 +6,8 @@ lfs = require 'lfs'
 import Scope from require 'alv.scope'
 import Module from require 'alv.module'
 import Error from require 'alv.error'
-import Result from require 'alv.result'
-import ValueStream from require 'alv.stream'
+import RTNode from require 'alv.rtnode'
+import Constant from require 'alv.result'
 
 export COPILOT
 
@@ -41,12 +41,12 @@ class Copilot
 
   --- require a module.
   -- @tparam string name
-  -- @treturn Result result
+  -- @treturn RTNode root
   require: (name) =>
     Error.wrap "loading module '#{name}'", ->
       ok, lua = pcall require, "alv-lib.#{name}"
       if ok
-        Result value: ValueStream.wrap lua
+        RTNode value: Constant.wrap lua
       else
         assert @modules, "no current eval cycle?"
         if mod = @modules[name]
diff --git a/alv/init.moon b/alv/init.moon
index f2fed2f..95432f3 100644
--- a/alv/init.moon
+++ b/alv/init.moon
@@ -13,8 +13,9 @@ cycle = require 'alv.cycle'
 
 version = require 'alv.version'
 import Logger from require 'alv.logger'
-import ValueStream, EventStream, IOStream from require 'alv.stream'
-import Result from require 'alv.result'
+
+import Constant, SigStream, EvtStream, IOStream from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 import Scope from require 'alv.scope'
 import Error from require 'alv.error'
 import Registry, SimpleRegistry from require 'alv.registry'
@@ -34,10 +35,11 @@ import Copilot from require 'alv.copilot'
 --- exports
 -- @table exports
 -- @tfield version version
--- @tfield ValueStream ValueStream
--- @tfield EventStream EventStream
+-- @tfield Constant Constant
+-- @tfield SigStream SigStream
+-- @tfield EvtStream EvtStream
 -- @tfield IOStream IOStream
--- @tfield Result Result
+-- @tfield RTNode RTNode
 -- @tfield Cell Cell
 -- @tfield RootCell RootCell
 -- @tfield Scope Scope
@@ -51,9 +53,9 @@ import Copilot from require 'alv.copilot'
 {
   :version
 
-  :ValueStream, :EventStream, :IOStream
+  :Constant, :SigStream, :EvtStream, :IOStream
   :Cell, :RootCell
-  :Result, :Scope, :Error
+  :RTNode, :Scope, :Error
 
   :Registry, :SimpleRegistry, :Tag
 
diff --git a/alv/invoke.moon b/alv/invoke.moon
index 439af49..4d9dfc9 100644
--- a/alv/invoke.moon
+++ b/alv/invoke.moon
@@ -2,10 +2,15 @@
 -- Builtins for invoking `Op`s and `FnDef`s.
 --
 -- @module invoke
-import Result from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 import Builtin from require 'alv.base'
 import Scope from require 'alv.scope'
 import Error from require 'alv.error'
+import Primitive from require 'alv.types'
+
+opdef = Primitive 'opdef'
+fndef = Primitive 'fndef'
+sym = Primitive 'sym'
 
 get_name = (value, raw) ->
   meta = if value.meta then value.meta.name
@@ -34,7 +39,7 @@ class op_invoke extends Builtin
       @op = prev.op\fork!
       prev.forked = COPILOT.T
     else
-      def = @head\unwrap 'opdef', "cant op-invoke #{@head}"
+      def = @head\unwrap opdef, "cant op-invoke #{@head}"
       @op = def!
 
   --- `Builtin:destroy` implementation.
@@ -50,11 +55,11 @@ class op_invoke extends Builtin
   -- checks if any of `op`:@{Op:all_inputs|all_inputs} are @{Input:dirty|dirty},
   -- and if so, calls `op`:@{Op:tick|tick}.
   --
-  -- The `Result` contains `op`, `Op.value` and all the `Result`s from the tail.
+  -- The `RTNode` contains `op`, `Op.value` and all the `RTNode`s from the tail.
   --
   -- @tparam Scope scope the active scope
   -- @tparam {AST,...} tail the arguments to this expression
-  -- @treturn Result
+  -- @treturn RTNode
   eval: (scope, tail) =>
     children = [L\push expr\eval, scope for expr in *tail]
 
@@ -73,7 +78,7 @@ class op_invoke extends Builtin
     for input in @op\all_inputs!
       input\finish_setup!
 
-    Result :children, value: @op.out, op: @op
+    RTNode :children, value: @op.out, op: @op
 
   --- The `Op` instance.
   --
@@ -92,18 +97,18 @@ class fn_invoke extends Builtin
   -- `FnDef.body` with the prefix `Builtin.tag`, and `AST:eval`s it in the newly
   -- created `Scope`.
   --
-  -- The `Result` contains the `Stream` from the cloned AST, and its children
-  -- are all the `Result`s from evaluating the tail as well as the cloned
+  -- The `RTNode` contains the `Stream` from the cloned AST, and its children
+  -- are all the `RTNode`s from evaluating the tail as well as the cloned
   -- `AST`s.
   --
   -- @tparam Scope caller_scope the active scope
   -- @tparam {AST,...} tail the arguments to this expression
-  -- @treturn Result the result of this evaluation
+  -- @treturn RTNode the result of this evaluation
   eval: (caller_scope, tail) =>
     name = get_name @head, @cell\head!
     frame = "invoking function #{name} at [#{@tag}]"
 
-    fndef = @head\unwrap 'fndef', "cant fn-invoke #{@head}"
+    fndef = @head\unwrap fndef, "cant fn-invoke #{@head}"
     { :params, :body } = fndef
     if #params != #tail
       err = Error 'argument', "expected #{#params} arguments, found #{#tail}"
@@ -113,7 +118,7 @@ class fn_invoke extends Builtin
     fn_scope = Scope fndef.scope, caller_scope
 
     children = for i=1,#params
-      name = params[i]\unwrap 'sym'
+      name = params[i]\unwrap sym
       with L\push tail[i]\eval, caller_scope
         fn_scope\set name, \make_ref!
 
@@ -121,7 +126,7 @@ class fn_invoke extends Builtin
     result = Error.wrap frame, clone\eval, fn_scope
 
     table.insert children, result
-    Result :children, value: result.value
+    RTNode :children, value: result.value
 
 {
   :op_invoke, :fn_invoke
diff --git a/alv/parsing.moon b/alv/parsing.moon
index f9d6f98..9cc46d7 100644
--- a/alv/parsing.moon
+++ b/alv/parsing.moon
@@ -2,7 +2,7 @@
 -- Lpeg Grammar for parsing `alive` code.
 --
 -- @module parsing
-import ValueStream from require 'alv.stream'
+import Constant from require 'alv.result'
 import Cell from require 'alv.cell'
 import Tag from require 'alv.tag'
 import R, S, P, V, C, Ct from require 'lpeg'
@@ -20,15 +20,15 @@ mspace = (comment + wc)^0 / 1            -- optional whitespace
 -- atoms
 digit = R '09'
 first = (R 'az', 'AZ') + S '-_+*/.!?=%'
-sym = first * (first + digit)^0 / ValueStream\parse 'sym'
+sym = first * (first + digit)^0 / Constant\parse 'sym'
 
-strd = '"' * (C ((P '\\"') + (P '\\\\') + (1 - P '"'))^0) * '"' / ValueStream\parse 'str', '\"'
-strq = "'" * (C ((P "\\'") + (P '\\\\') + (1 - P "'"))^0) * "'" / ValueStream\parse 'str', '\''
+strd = '"' * (C ((P '\\"') + (P '\\\\') + (1 - P '"'))^0) * '"' / Constant\parse 'str', '\"'
+strq = "'" * (C ((P "\\'") + (P '\\\\') + (1 - P "'"))^0) * "'" / Constant\parse 'str', '\''
 str = strd + strq
 
 int = digit^1
 float = (digit^1 * '.' * digit^0) + (digit^0 * '.' * digit^1)
-num = ((P '-')^-1 * (float + int)) / ValueStream\parse 'num'
+num = ((P '-')^-1 * (float + int)) / Constant\parse 'num'
 
 atom = num + sym + str
 
diff --git a/alv/stream/base.moon b/alv/result/base.moon
index 37cc8a4..26af4b4 100644
--- a/alv/stream/base.moon
+++ b/alv/result/base.moon
@@ -1,7 +1,7 @@
 ----
 -- base Stream interface.
 --
--- implemented by `ValueStream`, `EventStream`, and `IOStream`.
+-- implemented by `Constant`, `SigStream`, `EvtStream`, and `IOStream`.
 --
 -- @classmod Stream
 
@@ -9,7 +9,7 @@ class Stream
 --- Stream interface.
 --
 -- Methods that have to be implemented by `Stream` implementations
--- (`ValueStream`, `EventStream`, `IOStream`).
+-- (`SigStream`, `EvtStream`, `IOStream`).
 --
 -- @section interface
 
@@ -25,6 +25,9 @@ class Stream
   -- @function fork
   -- @treturn Stream
 
+  __tostring: => "<#{@type}#{@metatype} #{@type\pp @value}>"
+  __inherited: (cls) => cls.__base.__tostring or= @__tostring
+
   --- the type name of this Stream's value.
   --
   -- the following builtin typenames are used:
@@ -41,6 +44,13 @@ class Stream
   --
   -- @tfield string type
 
+  --- the metatype string for this Stream.
+  --
+  -- one of `=` (`Constant`), `~` (`SigStream`),
+  -- `!` (`EvtStream` and `IOStream`).
+  --
+  -- @tfield string type
+
   --- documentation metadata.
   --
   -- an optional table containing metadata for error messages and
diff --git a/alv/stream/value.moon b/alv/result/const.moon
index 3409537..10bc943 100644
--- a/alv/stream/value.moon
+++ b/alv/result/const.moon
@@ -1,13 +1,19 @@
 ----
--- Continuous stream of values.
+-- Constant Value.
 --
--- Implements the `Stream` and `AST` intefaces.
+-- Implements the `Stream` and `AST` inteface.
 --
--- @classmod ValueStream
-import Stream from require 'alv.stream.base'
-import Result from require 'alv.result'
+-- @classmod Constant
+import Stream from require 'alv.result.base'
+import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
 import scope, base from require 'alv.cycle'
+import Primitive from require 'alv.types'
+
+num = Primitive 'num'
+str = Primitive 'str'
+sym = Primitive 'sym'
+bool = Primitive 'bool'
 
 ancestor = (klass) ->
   assert klass, "cant find the ancestor of nil"
@@ -15,22 +21,11 @@ ancestor = (klass) ->
     klass = klass.__parent
   klass
 
-class ValueStream extends Stream
---- members
--- @section members
-
-  --- return whether this stream was changed in the current tick.
+class Constant extends Stream
+  --- Whether this Result is dirty.
   --
-  -- @treturn bool
-  dirty: => @updated == COPILOT.T
-
-  --- update this stream's value.
-  --
-  -- Marks this stream as dirty for the remainder of the current tick.
-  set: (value) =>
-    if value != @value
-      @value = value
-      @updated = COPILOT.T
+  -- @tresult bool always `false`.
+  dirty: => false
 
   --- unwrap to the Lua type.
   --
@@ -47,67 +42,25 @@ class ValueStream extends Stream
   --
   -- Used to insulate eval-cycles from each other.
   --
-  -- @treturn ValueStream
-  fork: =>
-    with ValueStream @type, @value, @raw
-      .updated = @updated
+  -- @treturn Constant
+  fork: => @
 
   --- alias for `unwrap`.
   __call: (...) => @unwrap ...
 
   --- compare two values.
   --
-  -- Compares two `ValueStream`s by comparing their types and their Lua values.
+  -- Compares two `SigStream`s by comparing their types and their Lua values.
   __eq: (other) => other.type == @type and other.value == @value
 
-  __tostring: =>
-    value = if @meta.name
-      @meta.name
-    else if 'table' == (type @value) and rawget @value, '__base'
-      @value.__name
-    else
-      tostring @value
-    "<#{@@__name} #{@type}: #{value}>"
-
   --- Stream metatype.
   --
-  -- @tfield string metatype
-  metatype: 'value'
-
-  --- the type name of this stream.
-  --
-  -- the following builtin typenames are used:
-  --
-  -- - `str` - strings, `value` is a Lua string
-  -- - `sym` - symbols, `value` is a Lua string
-  -- - `num` - numbers, `value` is a Lua number
-  -- - `bool` - booleans, `value` is a Lua boolean
-  -- - `bang` - trigger signals, `value` is a Lua boolean
-  -- - `opdef` - `value` is an `Op` subclass
-  -- - `builtin` - `value` is a `Builtin` subclass
-  -- - `fndef` - `value` is a `FnDef` instance
-  -- - `scope` - `value` is a `Scope` instance
-  --
-  -- @tfield string type
-
-  --- the wrapped Lua value.
-  -- @tfield any value
-
-  --- documentation metadata.
-  --
-  -- an optional table containing metadata for error messages and
-  -- documentation. The following keys are recognized:
-  --
-  -- - `name`: optional name
-  -- - `summary`: single-line description (markdown)
-  -- - `examples`: optional list of single-line code examples
-  -- - `description`: optional full-text description (markdown)
-  --
-  -- @tfield ?table meta
+  -- @tfield string metatype (`=`)
+  metatype: '='
 
 --- AST interface
 --
--- `ValueStream` implements the `AST` interface.
+-- `SignStream` implements the `AST` interface.
 -- @section ast
 
   --- evaluate this literal constant.
@@ -117,12 +70,14 @@ class ValueStream extends Stream
   -- Resolves `sym`s in `scope` and returns a reference to them.
   --
   -- @tparam Scope scope the scope to evaluate in
-  -- @treturn Result the evaluation result
+  -- @treturn RTNode the evaluation result
   eval: (scope) =>
+    return RTNode value: @ if @literal
+
     switch @type
-      when 'num', 'str'
-        Result value: @
-      when 'sym'
+      when num, str
+        RTNode value: @
+      when sym
         Error.wrap "resolving symbol '#{@value}'", scope\get, @value
       else
         error "cannot evaluate #{@}"
@@ -132,17 +87,17 @@ class ValueStream extends Stream
   -- Throws an error if `raw` is not set.
   --
   -- @treturn string the exact string this stream was parsed from
-  stringify: => assert @raw, "stringifying ValueStream that wasn't parsed"
+  stringify: => @raw
 
   --- clone this literal constant.
   --
-  -- @treturn ValueStream self
+  -- @treturn SignStream self
   clone: (prefix) => @
 
 --- static functions
 -- @section static
 
-  --- construct a new ValueStream.
+  --- construct a new Constant.
   --
   -- @classmethod
   -- @tparam string type the type name
@@ -157,9 +112,9 @@ class ValueStream extends Stream
   -- @tparam string sep the seperator char (only for `str`)
   @parse: (type, sep) =>
     switch type
-      when 'num' then (match) -> @ 'num', (tonumber match), match
-      when 'sym' then (match) -> @ 'sym', match, match
-      when 'str' then (match) -> @ 'str', (unescape match), sep .. match .. sep
+      when 'num' then (match) -> @ num, (tonumber match), match
+      when 'sym' then (match) -> @ sym, match, match
+      when 'str' then (match) -> @ str, (unescape match), sep .. match .. sep
 
   --- wrap a Lua value.
   --
@@ -167,7 +122,7 @@ class ValueStream extends Stream
   --
   -- @tparam any val the value to wrap
   -- @tparam[opt] string name the name of this value (for error logging)
-  -- @treturn ValueStream
+  -- @treturn Constant
   @wrap: (val, name='(unknown)') ->
     typ = switch type val
       when 'number' then 'num'
@@ -190,46 +145,52 @@ class ValueStream extends Stream
               error "#{name}: cannot wrap '#{val.__class.__name}' instance"
         else
           -- plain table
-          return ValueStream 'scope', scope.Scope.from_table val
+          val = scope.Scope.from_table val
+          'scope'
       else
         error "#{name}: cannot wrap Lua type '#{type val}'"
 
-    ValueStream typ, val
+    Constant (Primitive typ), val
 
   --- create a constant number.
-  -- @tparam number num the number
-  -- @treturn ValueStream
-  @num: (num) -> ValueStream 'num', num, tostring num
+  -- @tparam number val the number
+  -- @treturn Constant
+  @num: (val) -> Constant num, val, tostring val
 
   --- create a constant string.
-  -- @tparam string str the string
-  -- @treturn ValueStream
-  @str: (str) -> ValueStream 'str', str, "'#{str}'"
+  -- @tparam string val the string
+  -- @treturn Constant
+  @str: (val) -> Constant str, val, "'#{val}'"
 
   --- create a constant symbol.
-  -- @tparam string sym the symbol
-  -- @treturn ValueStream
-  @sym: (sym) -> ValueStream 'sym', sym, sym
+  -- @tparam string val the symbol
+  -- @treturn Constant
+  @sym: (val) -> Constant sym, val, val
 
   --- create a constant boolean.
-  -- @tparam boolean bool the boolean
-  -- @treturn ValueStream
-  @bool: (bool) -> ValueStream 'bool', bool, tostring bool
+  -- @tparam boolean val the boolean
+  -- @treturn Constant
+  @bool: (val) -> Constant bool, val, tostring val
+
+  --- create a forced-literal Constant.
+  --
+  -- For internal use in `Builtin`s only.
+  --
+  -- @treturn Constant
+  @literal: (...) ->
+    with Constant ...
+      .literal = true
 
   --- wrap and document a value.
   --
   -- wraps `args.value` using `wrap`, then assigns `meta`.
   --
   -- @tparam table args table with keys `value` and `meta`
-  -- @treturn ValueStream
+  -- @treturn Constant
   @meta: (args) ->
-    with ValueStream.wrap args.value
+    with Constant.wrap args.value
       .meta = args.meta if args.meta
 
-class LiteralValue extends ValueStream
-  eval: => Result value: @
-
 {
-  :ValueStream
-  :LiteralValue
+  :Constant
 }
diff --git a/alv/stream/event.moon b/alv/result/evt.moon
index 16716be..0559a70 100644
--- a/alv/stream/event.moon
+++ b/alv/result/evt.moon
@@ -1,13 +1,10 @@
 ----
 -- Stream of momentary events.
 --
--- @classmod EventStream
-import Stream from require 'alv.stream.base'
-import Result from require 'alv.result'
-import Error from require 'alv.error'
-import scope, base from require 'alv.cycle'
+-- @classmod EvtStream
+import Stream from require 'alv.result.base'
 
-class EventStream extends Stream
+class EvtStream extends Stream
 --- members
 -- @section members
 
@@ -44,19 +41,17 @@ class EventStream extends Stream
   --
   -- Used to wrap insulate eval-cycles from each other.
   --
-  -- @treturn EventStream
+  -- @treturn EvtStream
   fork: => @@ @type
 
   --- alias for `unwrap`.
   __call: (...) => @unwrap ...
-
-  __tostring: =>
-    "<#{@@__name} #{@type}>"
+  __tostring: => "<#{@type}#{@metatype} #{@type\pp @value}>"
 
   --- Stream metatype.
   --
-  -- @tfield string metatype
-  metatype: 'event'
+  -- @tfield string metatype (`!`)
+  metatype: '!'
 
   --- the type name of the stream.
   --
@@ -89,12 +84,12 @@ class EventStream extends Stream
 --- static functions
 -- @section static
 
-  --- construct a new EventStream.
+  --- construct a new EvtStream.
   --
   -- @classmethod
   -- @tparam string type the type name
   new: (type) => super type
 
 {
-  :EventStream
+  :EvtStream
 }
diff --git a/alv/result/init.moon b/alv/result/init.moon
new file mode 100644
index 0000000..aa7a115
--- /dev/null
+++ b/alv/result/init.moon
@@ -0,0 +1,21 @@
+----
+-- `Stream` interface and implementations.
+--
+-- @see Stream
+-- @see Constant
+-- @see SigStream
+-- @see EvtStream
+-- @see IOStream
+--
+-- @module stream
+import Constant from require 'alv.result.const'
+import SigStream from require 'alv.result.sig'
+import EvtStream from require 'alv.result.evt'
+import IOStream from require 'alv.result.io'
+
+{
+  :Constant
+  :SigStream
+  :EvtStream
+  :IOStream
+}
diff --git a/alv/stream/io.moon b/alv/result/io.moon
index e17daa8..b12322c 100644
--- a/alv/stream/io.moon
+++ b/alv/result/io.moon
@@ -4,12 +4,12 @@
 -- Unlike other `Stream`s, this is not updated/set by an `Op` instace, but is
 -- continuously polled for changes by the runtime and may mark itself as
 -- *dirty* at any point in time. All runtime execution happens due to IOStream
--- updates, which ripple through the `Result` tree.
+-- updates, which ripple through the `RTNode` tree.
 --
 -- @classmod IOStream
-import EventStream from require 'alv.stream.event'
+import EvtStream from require 'alv.result.evt'
 
-class IOStream extends EventStream
+class IOStream extends EvtStream
 --- IOStream interface.
 --
 -- methods that have to be implemented by `IOStream` implementations.
@@ -42,13 +42,13 @@ class IOStream extends EventStream
   -- via `Input.hot` should be notified (via `Op:tick`). May be called multiple
   -- times. May be called before `poll` on the first frame after construction.
   --
-  -- If this is not overrided, the `EventStream` interface can be used, see
-  -- `EventStream.add`, `EventStream.unwrap`, and `EventStream.dirty`.
+  -- If this is not overriden, the `EvtStream` interface can be used, see
+  -- `EvtStream.add`, `EvtStream.unwrap`, and `EvtStream.dirty`.
   --
   -- @function dirty
   -- @treturn bool whether processing is required
 
-  __inherited: (cls) => cls.__base.__tostring = @__tostring
+  __inherited: (cls) => cls.__base.__tostring or= @__tostring
 
 {
   :IOStream
diff --git a/alv/result/sig.moon b/alv/result/sig.moon
new file mode 100644
index 0000000..d7c18a3
--- /dev/null
+++ b/alv/result/sig.moon
@@ -0,0 +1,121 @@
+----
+-- Continuous stream of values.
+--
+-- @classmod SigStream
+import Stream from require 'alv.result.base'
+import Primitive from require 'alv.types'
+
+class SigStream extends Stream
+--- members
+-- @section members
+
+  --- return whether this stream was changed in the current tick.
+  --
+  -- @treturn bool
+  dirty: => @updated == COPILOT.T
+
+  --- update this stream's value.
+  --
+  -- Marks this stream as dirty for the remainder of the current tick.
+  set: (value) =>
+    if value != @value
+      @value = value
+      @updated = COPILOT.T
+
+  --- unwrap to the Lua type.
+  --
+  -- Asserts `@type == type` if `type` is given.
+  --
+  -- @tparam[opt] string type the type to check for
+  -- @tparam[optchain] string msg message to throw if type don't match
+  -- @treturn any `value`
+  unwrap: (type, msg) =>
+    assert type == @type, msg or "#{@} is not a #{type}" if type
+    @value
+
+  --- create a mutable copy of this stream.
+  --
+  -- Used to insulate eval-cycles from each other.
+  --
+  -- @treturn SigStream
+  fork: =>
+    with @@ @type, @value
+      .updated = @updated
+
+  --- alias for `unwrap`.
+  __call: (...) => @unwrap ...
+
+  --- compare two values.
+  --
+  -- Compares two `SigStream`s by comparing their types and their Lua values.
+  __eq: (other) => other.type == @type and other.value == @value
+
+  --- Stream metatype.
+  --
+  -- @tfield string metatype (`~`)
+  metatype: '~'
+
+  --- the type name of this stream.
+  --
+  -- the following builtin typenames are used:
+  --
+  -- - `str` - strings, `value` is a Lua string
+  -- - `sym` - symbols, `value` is a Lua string
+  -- - `num` - numbers, `value` is a Lua number
+  -- - `bool` - booleans, `value` is a Lua boolean
+  -- - `bang` - trigger signals, `value` is a Lua boolean
+  -- - `opdef` - `value` is an `Op` subclass
+  -- - `builtin` - `value` is a `Builtin` subclass
+  -- - `fndef` - `value` is a `FnDef` instance
+  -- - `scope` - `value` is a `Scope` instance
+  --
+  -- @tfield string type
+
+  --- the wrapped Lua value.
+  -- @tfield any value
+
+  --- documentation metadata.
+  --
+  -- an optional table containing metadata for error messages and
+  -- documentation. The following keys are recognized:
+  --
+  -- - `name`: optional name
+  -- - `summary`: single-line description (markdown)
+  -- - `examples`: optional list of single-line code examples
+  -- - `description`: optional full-text description (markdown)
+  --
+  -- @tfield ?table meta
+
+--- static functions
+-- @section static
+
+  --- construct a new SigStream.
+  --
+  -- @classmethod
+  -- @tparam string type the type name
+  -- @tparam any value the Lua value to be accessed through `unwrap`
+  new: (type, @value) => super type
+
+  --- create a number stream.
+  -- @tparam number val the number
+  -- @treturn SigStream
+  @num: (val) -> SigStream Primitive'num', val
+
+  --- create a string stream.
+  -- @tparam string val the string
+  -- @treturn SigStream
+  @str: (val) -> SigStream Primitive'str', val
+
+  --- create a symbol stream.
+  -- @tparam string val the symbol
+  -- @treturn symbol
+  @sym: (val) -> SigStream Primitive'sym', val
+
+  --- create a boolean stream.
+  -- @tparam boolean val the boolean
+  -- @treturn SigStream
+  @bool: (val) -> SigStream Primitive'bool', val
+
+{
+  :SigStream
+}
diff --git a/alv/result.moon b/alv/rtnode.moon
index 6f5ea28..dab4507 100644
--- a/alv/result.moon
+++ b/alv/rtnode.moon
@@ -1,15 +1,15 @@
 ----
--- Result of evaluating an expression.
+-- RTNode of evaluating an expression.
 --
--- `Result`s form a tree that controls execution order and message passing
+-- `RTNode`s form a tree that controls execution order and message
 -- between `Op`s.
 --
--- @classmod Result
-class Result
+-- @classmod RTNode
+class RTNode
 --- members
 -- @section members
 
-  --- return whether this Result's value is const.
+  --- return whether this RTNode's value is const.
   is_const: => not next @side_inputs
 
   --- assert value-constness and return the value.
@@ -22,20 +22,20 @@ class Result
   --- assert this result has a value, return its type.
   -- @treturn string
   type: =>
-    assert @value, "Result with value expected"
+    assert @value, "RTNode with value expected"
     @value.type
 
   --- assert this result has a value, returns its metatype.
   -- @treturn string `"value"` or `"event"`
   metatype: =>
-    assert @value, "Result with value expected"
+    assert @value, "RTNode with value expected"
     @value.metatype
 
   --- create a copy of this result with value-copy semantics.
   -- the copy has the same @value and @side_inputs, but will not update
   -- anything on \tick.
   make_ref: =>
-    with Result value: @value
+    with RTNode value: @value
       .side_inputs = @side_inputs
 
   --- poll all IOStream instances that are effecting this (sub)tree.
@@ -73,7 +73,7 @@ class Result
       @op\tick!
 
   __tostring: =>
-    buf = "<result=#{@value}"
+    buf = "<RT=#{@value}"
     buf ..= " #{@op}" if @op
     buf ..= " (#{#@children} children)" if #@children > 0
     buf ..= ">"
@@ -87,11 +87,11 @@ class Result
   --
   -- @tfield ?Op op
 
-  --- list of child `Result`s from subexpressions
+  --- list of child `RTNode`s from subexpressions
   --
-  -- @tfield {}|{Result,...} children
+  -- @tfield {}|{RTNode,...} children
 
-  --- cached mapping of all `Stream`/`Input` pairs affecting this Result.
+  --- cached mapping of all `Stream`/`Input` pairs affecting this RTNode.
   --
   -- This is the union of all `children`s `side_inputs` and all `Input`s from
   -- `op` that are not the `value` of any child.
@@ -101,7 +101,7 @@ class Result
 --- static functions
 -- @section static
 
-  --- create a new Result.
+  --- create a new RTNode.
   -- @classmethod
   -- @param params table with optional keys op, value, children. default: {}
   new: (params={}) =>
@@ -122,5 +122,5 @@ class Result
           @side_inputs[input.stream] = input
 
 {
-  :Result
+  :RTNode
 }
diff --git a/alv/scope.moon b/alv/scope.moon
index 6a0e2a5..575c36e 100644
--- a/alv/scope.moon
+++ b/alv/scope.moon
@@ -1,10 +1,11 @@
 ----
--- Mapping from `sym`s to `Result`s.
+-- Mapping from `sym`s to `RTNode`s.
 --
 -- @classmod Scope
-import ValueStream from require 'alv.stream'
-import Result from require 'alv.result'
+import Constant from require 'alv.result'
+import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
+import Primitive from require 'alv.types'
 
 class Scope
 --- members
@@ -12,21 +13,21 @@ class Scope
 
   --- set a Lua value in the scope.
   --
-  -- wraps `val` in a `ValueStream` and `Result` before calling `set`.
+  -- wraps `val` in a `Constant` and `RTNode` before calling `set`.
   --
   -- @tparam string key
   -- @tparam any val
   set_raw: (key, val) =>
-    value = ValueStream.wrap val, key
-    @values[key] = Result :value
+    value = Constant.wrap val, key
+    @values[key] = RTNode :value
 
-  --- set a symbol to a `Result`.
+  --- set a symbol to a `RTNode`.
   --
   -- @tparam string key
-  -- @tparam Result val
+  -- @tparam RTNode val
   set: (key, val) =>
     L\trace "setting #{key} = #{val} in #{@}"
-    assert val.__class == Result, "expected #{key}=#{val} to be Result"
+    assert val.__class == RTNode, "expected #{key}=#{val} to be RTNode"
     assert val.value, Error 'type', "cannot define symbol to nil"
     assert not @values[key], Error 'type', "cannot redefine symbol '#{key}'!"
     @values[key] = val
@@ -42,7 +43,7 @@ class Scope
   --- resolve a key in this Scope.
   --
   -- @tparam string key the key to resolve
-  -- @treturn ?Result the value of the definition that was found, or `nil`
+  -- @treturn ?RTNode the value of the definition that was found, or `nil`
   get: (key) =>
     L\debug "checking for #{key} in #{@}"
     if val = @values[key]
@@ -56,7 +57,7 @@ class Scope
     child = @get start
     if not child
       error Error 'reference', "undefined symbol '#{start}'"
-    if child\type! != 'scope'
+    if child\type! != (Primitive 'scope')
       error Error 'reference', "'#{start}' is not a scope"
     child.value!\get rest, while_msg
 
@@ -104,7 +105,7 @@ class Scope
   --- convert a Lua table to a Scope.
   --
   -- `tbl` may contain more tables (or `Scope`s).
-  -- Uses `ValueStream.wrap` on the values recursively.
+  -- Uses `Constant.wrap` on the values recursively.
   --
   -- @tparam table tbl the table to convert
   -- @treturn Scope
diff --git a/alv/stream/init.moon b/alv/stream/init.moon
deleted file mode 100644
index f9393b0..0000000
--- a/alv/stream/init.moon
+++ /dev/null
@@ -1,18 +0,0 @@
-----
--- `Stream` interface and implementations.
---
--- @see Stream
--- @see ValueStream
--- @see EventStream
--- @see IOStream
---
--- @module stream
-import ValueStream from require 'alv.stream.value'
-import EventStream from require 'alv.stream.event'
-import IOStream from require 'alv.stream.io'
-
-{
-  :ValueStream
-  :EventStream
-  :IOStream
-}
diff --git a/alv/types.moon b/alv/types.moon
new file mode 100644
index 0000000..3fcf722
--- /dev/null
+++ b/alv/types.moon
@@ -0,0 +1,101 @@
+-- what do i need types for?
+--
+-- ## implementation side
+-- argument specs - without values
+-- output specs & output streams
+--  - evt outputs are created without values,
+--  - val outputs are created *with* values!
+--
+-- ## language side
+-- explicit casting
+
+-- Check whether two tables have all the same,
+-- and *only the same* keys.
+shared_shape = (a, b) ->
+  for key in pairs a
+    return false unless b[key]
+
+  for key in pairs b
+    return false unless a[key]
+
+  true
+
+same = (a, b) ->
+  return unless shared_shape a, b
+  for key, val in pairs a
+    return false unless val == b[key]
+
+  true
+
+class Type
+  __eq: (a, b) ->
+    if a.__class == b.__class
+      a.__class.__base.__self_eq a, b
+
+  __inherited: (cls) =>
+    cls.__base.__self_eq = cls.__base.__eq
+    cls.__base.__eq = @__eq
+
+class Primitive extends Type
+  new: (@type) =>
+
+  pp: (value) => tostring value
+
+  __eq: (other) => @type == other.type
+  __tostring: => @type
+
+class Struct extends Type
+  new: (@types) =>
+
+  --- create a new struct with a selection of keys
+  project: (keys) =>
+    types = {}
+    for key in *keys
+      types[key] = @types[key]
+    @@ types
+
+  pp: (value) =>
+    inner = table.concat ["#{k}: #{@types[k]\pp v}" for k, v in pairs value], ', '
+    "{#{inner}}"
+
+  __eq: (other) => same @types, other.types
+  __tostring: =>
+    inner = table.concat ["#{k}: #{v}" for k, v in pairs @types], ', '
+    "{#{inner}}"
+
+class Array extends Type
+  new: (@size, @type) =>
+
+  pp: (value) =>
+    inner = table.concat [@type\pp v for v in *value], ' '
+    "[#{inner}]"
+
+  __eq: (other) => @size == other.size and @type == other.type
+  __tostring: => "#{@type}[#{@size}]"
+
+"
+bool = Primitive 'bool'
+num = Primitive 'num'
+str = Primitive 'str'
+
+vec3 = Array 3, num
+noteevt = Struct { note: str, dur: num }
+
+assert.is.equal 'num[3]', tostring vec3
+assert.is.equal '{dur: num, note: str}', tostring noteevt
+
+assert.is.equal vec3 == Array 3, num
+assert.not.equal vec3, Array 3, str
+assert.is.equal noteevt, Struct { oct: num, note: str, dur: num }
+assert.not.equal noteevt, Struct { oct: num, note: str, dur: str }
+
+print Constant bool, false
+print SigStream vec3, { 0.5, 0.3, 0.7 }
+print EvtStream noteevt
+"
+
+{
+  :Primitive
+  :Array
+  :Struct
+}
diff --git a/spec/cell_spec.moon b/spec/cell_spec.moon
index 0b2ff64..de46245 100644
--- a/spec/cell_spec.moon
+++ b/spec/cell_spec.moon
@@ -1,15 +1,15 @@
 import do_setup from require 'spec.test_setup'
 import Cell, RootCell from require 'alv.cell'
-import ValueStream, Scope, Tag, SimpleRegistry, globals from require 'alv'
+import Constant, Scope, Tag, SimpleRegistry, globals from require 'alv'
 import Copilot from require 'alv.copilot'
 
 setup do_setup
 
 hello_world = Cell.parse Tag.parse('2'), {
-  '', (ValueStream.sym 'hello'), ' ', (ValueStream.str 'world'), ''
+  '', (Constant.sym 'hello'), ' ', (Constant.str 'world'), ''
 }
 two_plus_two = Cell.parse Tag.parse('3'), {
-  '', (ValueStream.sym '+'), ' ', (ValueStream.num 2), ' ', (ValueStream.num 2), ''
+  '', (Constant.sym '+'), ' ', (Constant.num 2), ' ', (Constant.num 2), ''
 }
 
 describe 'Cell', ->
@@ -18,8 +18,8 @@ describe 'Cell', ->
     with hello_world\clone parent
       it 'keeps children', ->
         assert.is.equal Cell, .__class
-        assert.is.equal (ValueStream.sym 'hello'), \head!
-        assert.is.same { ValueStream.str 'world' }, \tail!
+        assert.is.equal (Constant.sym 'hello'), \head!
+        assert.is.same { Constant.str 'world' }, \tail!
 
       it 'clones the tag', ->
         assert.is.equal hello_world.tag, .tag.original
@@ -31,8 +31,8 @@ describe 'Cell', ->
       assert.has.error -> cell\eval globals
 
     it 'evaluates its head', ->
-      head = ValueStream.sym 'trace'
-      cell = Cell.parse { '', head, ' ', (ValueStream.sym 'true'), '' }
+      head = Constant.sym 'trace'
+      cell = Cell.parse { '', head, ' ', (Constant.sym 'true'), '' }
 
       s = spy.on head, 'eval'
       cell\eval globals
@@ -45,10 +45,10 @@ describe 'RootCell', ->
 
   test 'head is always "do"', ->
     cell = Cell.parse_root {}
-    assert.is.equal (ValueStream.sym 'do'), cell\head!
+    assert.is.equal (Constant.sym 'do'), cell\head!
 
     cell = RootCell nil, { hello_world, two_plus_two }
-    assert.is.equal (ValueStream.sym 'do'), cell\head!
+    assert.is.equal (Constant.sym 'do'), cell\head!
 
   test 'tail is all children', ->
     cell = Cell.parse_root {}
diff --git a/spec/input_spec.moon b/spec/input_spec.moon
index 6ab4388..a8107ae 100644
--- a/spec/input_spec.moon
+++ b/spec/input_spec.moon
@@ -1,10 +1,13 @@
 import do_setup from require 'spec.test_setup'
-import Input, Result, ValueStream, EventStream, IOStream from require 'alv.base'
+import Input, Result, SigStream, EvtStream, IOStream from require 'alv.base'
+import Primitive from require 'alv.types'
 
 setup do_setup
 
+my_io = Primitive 'my-io'
+
 class MyIO extends IOStream
-  new: => super 'my-io'
+  new: => super my_io
   dirty: => @is_dirty
 
 basic_tests = (stream, input) ->
@@ -22,7 +25,7 @@ basic_tests = (stream, input) ->
     assert.is.equal stream.metatype, input\metatype!
 
 describe 'Input.cold', ->
-  stream = ValueStream.num 1
+  stream = SigStream.num 1
   input = Input.cold stream
 
   basic_tests stream, input
@@ -36,7 +39,7 @@ describe 'Input.cold', ->
     assert.is.false input\dirty!
     input\finish_setup!
 
-    new_input = Input.cold ValueStream.num 3
+    new_input = Input.cold SigStream.num 3
     new_input\setup input
     assert.is.false new_input\dirty!
     new_input.stream\set 4
@@ -44,8 +47,8 @@ describe 'Input.cold', ->
     input\finish_setup!
 
 describe 'Input.hot', ->
-  describe 'with EventStream', ->
-    stream = EventStream 'num'
+  describe 'with EvtStream', ->
+    stream = EvtStream Primitive 'num'
     input = Input.hot stream
 
     basic_tests stream, input
@@ -53,7 +56,7 @@ describe 'Input.hot', ->
     it 'is marked for lifting', ->
       assert.is.nil input.io
 
-    it 'is dirty when the EventStream is dirty', ->
+    it 'is dirty when the EvtStream is dirty', ->
       assert.is.false input\dirty!
       assert.is.false stream\dirty!
 
@@ -106,8 +109,8 @@ describe 'Input.hot', ->
       assert.is.true input\dirty!
       assert.is.true stream\dirty!
 
-  describe 'with ValueStream', ->
-    stream = ValueStream.num 1
+  describe 'with SigStream', ->
+    stream = SigStream.num 1
     local input
 
     describe 'at evaltime', ->
@@ -120,7 +123,7 @@ describe 'Input.hot', ->
         input\finish_setup!
 
       it 'is dirty when different', ->
-        newval = ValueStream.num 2
+        newval = SigStream.num 2
 
         assert.is.false newval\dirty!
         newinput = Input.hot newval
@@ -129,7 +132,7 @@ describe 'Input.hot', ->
         newinput\finish_setup!
 
       it 'is not dirty when equal', ->
-        newval = ValueStream.num!
+        newval = SigStream.num!
         newval\set 1
 
         assert.is.true newval\dirty!
diff --git a/spec/match_spec.moon b/spec/match_spec.moon
index 52911db..91cee02 100644
--- a/spec/match_spec.moon
+++ b/spec/match_spec.moon
@@ -1,14 +1,15 @@
 import val, evt from require 'alv.base.match'
-import Result, ValueStream, EventStream from require 'alv'
+import RTNode, SigStream, EvtStream from require 'alv'
+import Primitive from require 'alv.types'
 
 mk_val = (type, const) ->
-  value = ValueStream type
-  with Result :value
+  value = SigStream Primitive type
+  with RTNode :value
     .side_inputs = { 'fake' } unless const
 
 mk_evt = (type, const) ->
-  value = EventStream type
-  with Result :value
+  value = EvtStream Primitive type
+  with RTNode :value
     .side_inputs = { 'fake' } unless const
 
 describe 'val and evt', ->
diff --git a/spec/parsing_spec.moon b/spec/parsing_spec.moon
index ecc8ff3..0486276 100644
--- a/spec/parsing_spec.moon
+++ b/spec/parsing_spec.moon
@@ -1,64 +1,53 @@
 import space, atom, expr, explist, cell, program, comment
   from require 'alv.parsing'
-import ValueStream from require 'alv'
+import Constant from require 'alv'
 import Logger from require 'alv.logger'
 Logger\init 'silent'
 
-verify_parse = (parser, str) ->
-  with assert parser\match str
-    assert.is.equal str, \stringify!
+verify_parse = (parser, val) ->
+  with assert parser\match val
+    assert.is.equal val, \stringify!
 
-verify_parse_nope = (parser, str) ->
-  with assert parser\match str
-    without_nope = str\match '^(.*) nope$'
+verify_parse_nope = (parser, val) ->
+  with assert parser\match val
+    without_nope = val\match '^(.*) nope$'
     assert.is.equal without_nope, \stringify!
 
 describe 'atom parsing', ->
   test 'symbols', ->
     sym = verify_parse_nope atom, 'some-toast nope'
-    assert.is.equal 'sym', sym.type
-    assert.is.equal 'some-toast', sym\unwrap!
-    assert.is.equal 'some-toast', sym\stringify!
+    assert.is.equal (Constant.sym 'some-toast'), sym
 
   describe 'numbers', ->
     it 'parses ints', ->
       num = verify_parse_nope atom, '1234 nope'
-      assert.is.equal 'num', num.type
-      assert.is.equal 1234, num\unwrap!
-      assert.is.equal '1234', num\stringify!
+      assert.is.equal (Constant.num 1234), num
 
     it 'parses floats', ->
       num = verify_parse_nope atom, '0.123 nope'
-      assert.is.equal 'num', num.type
-      assert.is.equal 0.123, num\unwrap!
+      assert.is.equal (Constant.num 0.123), num
 
       num = verify_parse_nope atom, '.123 nope'
-      assert.is.equal 'num', num.type
-      assert.is.equal 0.123, num\unwrap!
+      assert.is.equal (Constant.num 0.123), num
 
       num = verify_parse_nope atom, '0. nope'
-      assert.is.equal 'num', num.type
-      assert.is.equal 0, num\unwrap!
+      assert.is.equal (Constant.num 0), num
 
   describe 'strings', ->
     it 'parses double-quote strings', ->
       str = verify_parse_nope atom, '"help some stuff!" nope'
-      assert.is.equal 'str', str.type
-      assert.is.equal 'help some stuff!', str\unwrap!
+      assert.is.equal (Constant.str 'help some stuff!'), str
 
     it 'parses single-quote strings', ->
       str = verify_parse_nope atom, "'help some stuff!' nope"
-      assert.is.equal 'str', str.type
-      assert.is.equal "help some stuff!", str\unwrap!
+      assert.is.equal (Constant.str "help some stuff!"), str
 
     it 'handles escapes', ->
       str = verify_parse_nope atom, '"string with \\"quote\\"s and \\\\" nope'
-      assert.is.equal 'str', str.type
-      assert.is.equal 'string with \"quote\"s and \\', str\unwrap!
+      assert.is.equal (Constant.str 'string with \"quote\"s and \\'), str
 
       str = verify_parse_nope atom, "'string with \\'quote\\'s and \\\\' nope"
-      assert.is.equal 'str', str.type
-      assert.is.equal "string with \'quote\'s and \\", str\unwrap!
+      assert.is.equal (Constant.str "string with \'quote\'s and \\"), str
 
 describe 'Cell', ->
   test 'basic parsing', ->
@@ -66,9 +55,9 @@ describe 'Cell', ->
                                 "friend" )'
 
     assert.is.equal 3, #node.children
-    assert.is.equal (ValueStream.num 3), node.children[1]
-    assert.is.equal (ValueStream.sym 'ok-yes'), node.children[2]
-    assert.is.equal (ValueStream.str 'friend'), node.children[3]
+    assert.is.equal (Constant.num 3), node.children[1]
+    assert.is.equal (Constant.sym 'ok-yes'), node.children[2]
+    assert.is.equal (Constant.str 'friend'), node.children[3]
 
   test 'tag parsing', ->
     node = verify_parse cell, '([42]tagged 2)'
@@ -89,8 +78,8 @@ describe 'RootCell parsing', ->
       node = verify_parse program, str
 
       assert.is.equal 2, #node.children
-      assert.is.equal (ValueStream.num 3), node.children[1]
-      assert.is.equal (ValueStream.sym 'ok-yes'), node.children[2]
+      assert.is.equal (Constant.num 3), node.children[1]
+      assert.is.equal (Constant.sym 'ok-yes'), node.children[2]
 
     it 'at the front of the string', ->
       verify ' 3\tok-yes'
diff --git a/spec/result/const_spec.moon b/spec/result/const_spec.moon
new file mode 100644
index 0000000..6bd7999
--- /dev/null
+++ b/spec/result/const_spec.moon
@@ -0,0 +1,149 @@
+import do_setup from require 'spec.test_setup'
+import Constant, RTNode, Scope, SimpleRegistry from require 'alv'
+import Op, Builtin from require 'alv.base'
+import Primitive from require 'alv.types'
+
+class TestOp extends Op
+  new: (...) => super ...
+
+class TestBuiltin extends Builtin
+  new: (...) =>
+
+setup do_setup
+
+describe 'Constant', ->
+  describe '.wrap', ->
+    it 'wraps numbers', ->
+      got = Constant.wrap 3
+      assert.is.equal (Primitive 'num'), got.type
+      assert.is.equal 3, got.value
+
+    it 'wraps strings', ->
+      got = Constant.wrap "im a happy string"
+      assert.is.equal (Primitive 'str'), got.type
+      assert.is.equal "im a happy string", got.value
+
+    it 'wraps Constants', ->
+      pi = Constant.num 3.14
+      got = Constant.wrap pi
+
+      assert.is.equal pi, got
+
+    it 'wraps Opdefs', ->
+      got = Constant.wrap TestOp
+
+      assert.is.equal (Primitive 'opdef'), got.type
+      assert.is.equal TestOp, got.value
+
+    it 'wraps Bultins', ->
+      got = Constant.wrap TestBuiltin
+
+      assert.is.equal (Primitive 'builtin'), got.type
+      assert.is.equal TestBuiltin, got.value
+
+    it 'wraps Scopes', ->
+      sub = Scope!
+      got = Constant.wrap sub
+
+      assert.is.equal (Primitive 'scope'), got.type
+      assert.is.equal sub, got.value
+
+    it 'wraps tables', ->
+      pi = Constant.num 3.14
+      got = Constant.wrap { :pi }
+
+      assert.is.equal (Primitive 'scope'), got.type
+      assert.is.equal pi, (got.value\get 'pi')\const!
+
+  describe ':unwrap', ->
+    it 'returns the raw value!', ->
+      assert.is.equal 3.14, (Constant.num 3.14)\unwrap!
+      assert.is.equal 'hi', (Constant.str 'hi')\unwrap!
+      assert.is.equal 'hi', (Constant.sym 'hi')\unwrap!
+
+    test 'can assert the type', ->
+      assert.is.equal 3.14, (Constant.num 3.14)\unwrap Primitive 'num'
+      assert.is.equal 'hi', (Constant.str 'hi')\unwrap Primitive 'str'
+      assert.is.equal 'hi', (Constant.sym 'hi')\unwrap Primitive 'sym'
+      assert.has_error -> (Constant.num 3.14)\unwrap Primitive 'sym'
+      assert.has_error -> (Constant.str 'hi')\unwrap Primitive 'num'
+      assert.has_error -> (Constant.sym 'hi')\unwrap Primitive 'str'
+
+    test 'has __call shorthand', ->
+      assert.is.equal 3.14, (Constant.num 3.14)!
+      assert.is.equal 'hi', (Constant.str 'hi')!
+      assert.is.equal 'hi', (Constant.sym 'hi')!
+      assert.is.equal 3.14, (Constant.num 3.14) Primitive 'num'
+      assert.is.equal 'hi', (Constant.str 'hi') Primitive 'str'
+      assert.is.equal 'hi', (Constant.sym 'hi') Primitive 'sym'
+      assert.has_error -> (Constant.num 3.14) Primitive 'sym'
+      assert.has_error -> (Constant.str 'hi') Primitive 'num'
+      assert.has_error -> (Constant.sym 'hi') Primitive 'str'
+
+  describe 'overrides __eq', ->
+    it 'compares the type', ->
+      val = Constant.num 3
+      assert.is.equal (Constant.num 3), val
+      assert.not.equal (Constant.str '3'), val
+
+      val = Constant.str 'hello'
+      assert.is.equal (Constant.str 'hello'), val
+      assert.not.equal (Constant.sym 'hello'), val
+
+    it 'compares the value', ->
+      val = Constant.num 3
+      assert.is.equal (Constant.num 3), val
+      assert.not.equal (Constant.num 4), val
+
+  it ':dirty is always false', ->
+    val = Constant.num 3
+    assert.is.false val\dirty!
+
+    val.value = 4
+    assert.is.false val\dirty!
+
+  describe ':eval', ->
+    it 'turns numbers into consts', ->
+      assert_noop = (val) ->
+        assert.is.equal val, val\eval!\const!
+
+      assert_noop Constant.num 2
+      assert_noop Constant.str 'hello'
+
+    it 'looks up symbols in the scope', ->
+      scope = with Scope!
+        \set 'number', RTNode value: Constant.num 3
+        \set 'hello', RTNode value: Constant.str "world"
+        \set 'goodbye', RTNode value: Constant.sym "again"
+
+      assert_eval = (sym, val) ->
+        const = Constant.sym sym
+        assert.is.equal val, (const\eval scope)\const!
+
+      assert_eval 'number', Constant.num 3
+      assert_eval 'hello', Constant.str "world"
+      assert_eval 'goodbye', Constant.sym "again"
+
+  it ':clones literals as themselves', ->
+    assert_noop = (val) -> assert.is.equal val, val\clone!
+
+    assert_noop Constant.num 2
+    assert_noop Constant.str 'hello'
+    assert_noop Constant.sym 'world'
+
+  describe ':fork', ->
+    it 'is equal to the original', ->
+      a = Constant.num 2
+      b = Constant.str 'asdf'
+      c = Constant (Primitive 'weird'), {}, '(raw)'
+
+      aa, bb, cc = a\fork!, b\fork!, c\fork!
+      assert.is.equal a, aa
+      assert.is.equal b, bb
+      assert.is.equal c, cc
+
+      assert.is.false aa\dirty!
+      assert.is.false bb\dirty!
+      assert.is.false cc\dirty!
+
+      assert.is.equal c.raw, cc.raw
diff --git a/spec/result/sig_spec.moon b/spec/result/sig_spec.moon
new file mode 100644
index 0000000..4bc0a67
--- /dev/null
+++ b/spec/result/sig_spec.moon
@@ -0,0 +1,109 @@
+import do_setup from require 'spec.test_setup'
+import SigStream, RTNode, Scope, SimpleRegistry from require 'alv'
+import Op, Builtin from require 'alv.base'
+import Primitive from require 'alv.types'
+
+class TestOp extends Op
+  new: (...) => super ...
+
+class TestBuiltin extends Builtin
+  new: (...) =>
+
+setup do_setup
+
+describe 'SigStream', ->
+  describe ':unwrap', ->
+    it 'returns the raw value!', ->
+      assert.is.equal 3.14, (SigStream.num 3.14)\unwrap!
+      assert.is.equal 'hi', (SigStream.str 'hi')\unwrap!
+      assert.is.equal 'hi', (SigStream.sym 'hi')\unwrap!
+
+    test 'can assert the type', ->
+      assert.is.equal 3.14, (SigStream.num 3.14)\unwrap Primitive 'num'
+      assert.is.equal 'hi', (SigStream.str 'hi')\unwrap Primitive 'str'
+      assert.is.equal 'hi', (SigStream.sym 'hi')\unwrap Primitive 'sym'
+      assert.has_error -> (SigStream.num 3.14)\unwrap Primitive 'sym'
+      assert.has_error -> (SigStream.str 'hi')\unwrap Primitive 'num'
+      assert.has_error -> (SigStream.sym 'hi')\unwrap Primitive 'str'
+
+    test 'has __call shorthand', ->
+      assert.is.equal 3.14, (SigStream.num 3.14)!
+      assert.is.equal 'hi', (SigStream.str 'hi')!
+      assert.is.equal 'hi', (SigStream.sym 'hi')!
+      assert.is.equal 3.14, (SigStream.num 3.14) Primitive 'num'
+      assert.is.equal 'hi', (SigStream.str 'hi') Primitive 'str'
+      assert.is.equal 'hi', (SigStream.sym 'hi') Primitive 'sym'
+      assert.has_error -> (SigStream.num 3.14) Primitive 'sym'
+      assert.has_error -> (SigStream.str 'hi') Primitive 'num'
+      assert.has_error -> (SigStream.sym 'hi') Primitive 'str'
+
+  describe 'overrides __eq', ->
+    it 'compares the type', ->
+      val = SigStream.num 3
+      assert.is.equal (SigStream.num 3), val
+      assert.not.equal (SigStream.str '3'), val
+
+      val = SigStream.str 'hello'
+      assert.is.equal (SigStream.str 'hello'), val
+      assert.not.equal (SigStream.sym 'hello'), val
+
+    it 'compares the value', ->
+      val = SigStream.num 3
+      assert.is.equal (SigStream.num 3), val
+      assert.not.equal (SigStream.num 4), val
+
+  describe ':set', ->
+    it 'sets the value', ->
+      val = SigStream.num 3
+      assert.is.equal (SigStream.num 3), val
+
+      val\set 4
+      assert.is.equal (SigStream.num 4), val
+      assert.not.equal (SigStream.num 3), val
+
+    it 'marks the value dirty', ->
+      val = SigStream.num 3
+      assert.is.false val\dirty!
+
+      val\set 4
+      assert.is.true val\dirty!
+
+  describe ':fork', ->
+    it 'is equal to the original', ->
+      a = SigStream.num 2
+      b = SigStream.str 'asdf'
+      c = with SigStream 'weird', {}, '(raw)'
+        \set {}
+
+      aa, bb, cc = a\fork!, b\fork!, c\fork!
+      assert.is.equal a, aa
+      assert.is.equal b, bb
+      assert.is.equal c, cc
+
+      assert.is.false aa\dirty!
+      assert.is.false bb\dirty!
+      assert.is.true cc\dirty!
+
+      assert.is.equal c.raw, cc.raw
+
+    it 'isolates the original from the fork', ->
+      a = SigStream.num 3
+      b = with SigStream 'weird', {}, '(raw)'
+        \set {}
+
+      aa, bb = a\fork!, b\fork!
+
+      bb\set {false}
+
+      assert.is.same {}, b!
+      assert.is.same {false}, bb!
+      assert.is.true b\dirty!
+      assert.is.true bb\dirty!
+
+      COPILOT\next_tick!
+      aa\set 4
+
+      assert.is.equal 3, a!
+      assert.is.equal 4, aa!
+      assert.is.false a\dirty!
+      assert.is.true aa\dirty!
diff --git a/spec/result_spec.moon b/spec/rtnode_spec.moon
index f7006f1..c4cf4e9 100644
--- a/spec/result_spec.moon
+++ b/spec/rtnode_spec.moon
@@ -1,44 +1,47 @@
 import do_setup from require 'spec.test_setup'
-import Result, Scope, SimpleRegistry from require 'alv'
-import Input, Op, ValueStream, EventStream, IOStream from require 'alv.base'
+import RTNode, Scope, SimpleRegistry from require 'alv'
+import Input, Op, Constant, EvtStream, IOStream from require 'alv.base'
+import Primitive from require 'alv.types'
 
 setup do_setup
+num = Primitive 'num'
+bang = Primitive 'bang'
 
 op_with_inputs = (inputs) ->
   with Op!
     \setup inputs if inputs
 
 result_with_sideinput = (value, input) ->
-  with Result :value
+  with RTNode :value
     .side_inputs = { [value]: input }
 
 class DirtyIO extends IOStream
-  new: => super 'dirty-io'
+  new: => super Primitive 'dirty-io'
   dirty: => true
 
-describe 'Result', ->
+describe 'RTNode', ->
   it 'wraps value, children', ->
-    value = ValueStream.num 3
+    value = Constant.num 3
 
-    a = Result!
-    b = Result!
+    a = RTNode!
+    b = RTNode!
     children = { a, b }
 
-    result = Result :value, :children
+    result = RTNode :value, :children
 
     assert.is.equal value, result.value
     assert.is.same children, result.children
 
   it ':type gets type and assets value', ->
-    result = Result value: ValueStream.num 2
-    assert.is.equal 'num', result\type!
+    result = RTNode value: Constant.num 2
+    assert.is.equal num, result\type!
 
-    result = Result!
+    result = RTNode!
     assert.has.error -> result\type!
 
   it ':is_const', ->
-    value = ValueStream.num 2
-    pure = Result :value
+    value = Constant.num 2
+    pure = RTNode :value
     impure = result_with_sideinput value, {}
 
     assert.is.true pure\is_const!
@@ -49,10 +52,10 @@ describe 'Result', ->
     assert.has.error (-> impure\const 'test'), 'test'
 
   it ':make_ref', ->
-    value = ValueStream.num 2
+    value = Constant.num 2
     input = Input.hot value
     op = op_with_inputs { input }
-    thick = Result :value, :op, children: { Result!, Result! }
+    thick = RTNode :value, :op, children: { RTNode!, RTNode! }
     ref = thick\make_ref!
 
     assert ref
@@ -62,43 +65,43 @@ describe 'Result', ->
     assert.is.nil ref.op
 
   it 'lifts up inputs from op', ->
-    event = ValueStream 'bang', false
+    event = Constant bang, false
     event_input = Input.hot event
 
-    value = ValueStream 'num', 4
+    value = Constant num, 4
     value_input = Input.hot value
 
     op = op_with_inputs { event_input, value_input }
-    result = Result op: op, :value
+    result = RTNode op: op, :value
 
     assert.is.equal op, result.op
     assert.is.same { [event]: event_input, [value]: value_input },
                    result.side_inputs
 
   it 'does not lift up op inputs that are also child values', ->
-    event = ValueStream 'bang', false
+    event = Constant bang, false
     event_input = Input.hot event
 
-    value = ValueStream 'num', 4
+    value = Constant num, 4
     value_input = Input.hot value
 
     op = op_with_inputs { event_input, value_input }
-    result = Result op: op, :value, children: { Result :value }
+    result = RTNode op: op, :value, children: { RTNode :value }
 
     assert.is.same { [event]: event_input }, result.side_inputs
 
   it 'lifts up side_inputs from children', ->
-    event_value = ValueStream 'bang', false
+    event_value = Constant bang, false
     event_input = Input.hot event_value
-    event = Result op: op_with_inputs { event_input }
+    event = RTNode op: op_with_inputs { event_input }
     assert.is.same { [event_value]: event_input }, event.side_inputs
 
-    value_value = ValueStream 'num', 4
+    value_value = Constant num, 4
     value_input = Input.hot value_value
-    value = Result op: op_with_inputs { value_input }
+    value = RTNode op: op_with_inputs { value_input }
     assert.is.same { [value_value]: value_input }, value.side_inputs
 
-    result = Result children: { event, value }
+    result = RTNode children: { event, value }
     assert.is.same { [event_value]: event_input, [value_value]: value_input },
                    result.side_inputs
 
@@ -106,11 +109,11 @@ describe 'Result', ->
     local a_value, a_child, a_input
     local b_value, b_child, b_input
     before_each ->
-      a_value = EventStream 'num'
+      a_value = EvtStream num
       a_input = Input.hot a_value
       a_child = result_with_sideinput a_value, a_input
 
-      b_value = EventStream 'num'
+      b_value = EvtStream num
       b_input = Input.hot b_value
       b_child = result_with_sideinput b_value, b_input
 
@@ -122,7 +125,7 @@ describe 'Result', ->
       a = spy.on a_child, 'tick'
       b = spy.on b_child, 'tick'
 
-      result = Result children: { a_child, b_child }
+      result = RTNode children: { a_child, b_child }
       result\tick!
 
       assert.spy(a).was_called_with match.ref a_child
@@ -135,7 +138,7 @@ describe 'Result', ->
       a = spy.on a_child, 'tick'
       b = spy.on b_child, 'tick'
 
-      result = Result children: { a_child, b_child }
+      result = RTNode children: { a_child, b_child }
       result\tick!
 
       assert.spy(a).was_not_called!
@@ -149,7 +152,7 @@ describe 'Result', ->
       op = op_with_inputs a: Input.hot a_value
       s = spy.on op, 'tick'
 
-      result = Result :op, children: { a_child, b_child }
+      result = RTNode :op, children: { a_child, b_child }
       result\tick!
 
       assert.spy(s).was_called_with match.ref op
@@ -162,7 +165,7 @@ describe 'Result', ->
       op = op_with_inputs { Input.hot b_value }
       s = spy.on op, 'tick'
 
-      result = Result :op, children: { a_child, b_child }
+      result = RTNode :op, children: { a_child, b_child }
       result\tick!
 
       assert.spy(s).was_not_called!
@@ -172,7 +175,7 @@ describe 'Result', ->
       io = DirtyIO!
       input = Input.hot io
       op = op_with_inputs { input }
-      result = Result :op
+      result = RTNode :op
 
       s = spy.on io, 'poll'
       assert.is.same { [io]: input }, result.side_inputs
diff --git a/spec/scope_spec.moon b/spec/scope_spec.moon
index beeeeac..405e9f8 100644
--- a/spec/scope_spec.moon
+++ b/spec/scope_spec.moon
@@ -1,4 +1,5 @@
-import Scope, ValueStream, Result from require 'alv'
+import Scope, Constant, RTNode from require 'alv'
+import Primitive from require 'alv.types'
 import Op from require 'alv.base'
 import Logger from require 'alv.logger'
 Logger\init 'silent'
@@ -6,7 +7,12 @@ Logger\init 'silent'
 class TestOp extends Op
   new: (...) => super ...
 
-wrap_res = (value) -> Result :value
+wrap_res = (value) -> RTNode :value
+
+num = Primitive 'num'
+str = Primitive 'str'
+opdef = Primitive 'opdef'
+scope_t = Primitive 'scope'
 
 describe 'Scope', ->
   describe 'constifies', ->
@@ -16,18 +22,18 @@ describe 'Scope', ->
       scope\set_raw 'num', 3
 
       got = (scope\get 'num')\const!
-      assert.is.equal 'num', got.type
+      assert.is.equal num, got.type
       assert.is.equal 3, got.value
 
     test 'strings', ->
       scope\set_raw 'str', "im a happy string"
 
       got = (scope\get 'str')\const!
-      assert.is.equal 'str', got.type
+      assert.is.equal str, got.type
       assert.is.equal "im a happy string", got.value
 
     test 'Values', ->
-      pi = ValueStream 'num', 3.14
+      pi = Constant.num 3.14
       scope\set_raw 'pi', pi
 
       assert.is.equal pi, (scope\get 'pi')\const!
@@ -36,7 +42,7 @@ describe 'Scope', ->
       scope\set_raw 'test', TestOp
 
       got = (scope\get 'test')\const!
-      assert.is.equal 'opdef', got.type
+      assert.is.equal opdef, got.type
       assert.is.equal TestOp, got.value
 
     test 'Scopes', ->
@@ -44,21 +50,21 @@ describe 'Scope', ->
       scope\set_raw 'sub', sub
 
       got = (scope\get 'sub')\const!
-      assert.is.equal 'scope', got.type
+      assert.is.equal scope_t, got.type
       assert.is.equal sub, got.value
 
     test 'tables', ->
-      pi = ValueStream 'num', 3.14
-      scope\set_raw 'math',  { :pi }
+      pi = Constant.num 3.14
+      scope\set_raw 'math', { :pi }
 
       got = (scope\get 'math')\const!
-      assert.is.equal 'scope', got.type
+      assert.is.equal scope_t, got.type
       assert.is.equal Scope, got.value.__class
       assert.is.equal pi, (got.value\get 'pi')\const!
       assert.is.equal pi, (scope\get 'math/pi')\const!
 
   it 'wraps Values in from_table', ->
-    pi = ValueStream 'num', 3.14
+    pi = Constant.num 3.14
     scope = Scope.from_table {
       num: 3
       str: "im a happy string"
@@ -68,21 +74,21 @@ describe 'Scope', ->
     }
 
     got = (scope\get 'num')\const!
-    assert.is.equal 'num', got.type
+    assert.is.equal num, got.type
     assert.is.equal 3, got.value
 
     got = (scope\get 'str')\const!
-    assert.is.equal 'str', got.type
+    assert.is.equal str, got.type
     assert.is.equal "im a happy string", got.value
 
     assert.is.equal pi, (scope\get 'pi')\const!
 
     got = (scope\get 'test')\const!
-    assert.is.equal 'opdef', got.type
+    assert.is.equal opdef, got.type
     assert.is.equal TestOp, got.value
 
     got = (scope\get 'math')\const!
-    assert.is.equal 'scope', got.type
+    assert.is.equal scope_t, got.type
     assert.is.equal pi, (scope\get 'math/pi')\const!
 
   it 'gets from nested scopes', ->
@@ -90,7 +96,7 @@ describe 'Scope', ->
     a = Scope!
     b = Scope!
 
-    pi = ValueStream 'num', 3.14
+    pi = Constant.num 3.14
     b\set_raw 'test', pi
     a\set_raw 'child', b
     root\set_raw 'deep', a
@@ -98,8 +104,8 @@ describe 'Scope', ->
     assert.is.equal pi, (root\get 'deep/child/test')\const!
 
   describe 'can set symbols', ->
-    one = wrap_res ValueStream.num 1
-    two = wrap_res ValueStream.num 2
+    one = wrap_res Constant.num 1
+    two = wrap_res Constant.num 2
     scope = Scope!
 
     it 'disallows re-setting symbols', ->
@@ -119,14 +125,14 @@ describe 'Scope', ->
 
     it 'allows access', ->
       got = (scope\get 'inherited')\const!
-      assert.is.equal 'str', got.type
+      assert.is.equal str, got.type
       assert.is.equal "inherited string", got.value
 
     it 'can be shadowed', ->
       scope\set_raw 'hidden', "overwritten"
 
       got = (scope\get 'hidden')\const!
-      assert.is.equal 'str', got.type
+      assert.is.equal str, got.type
       assert.is.equal "overwritten", got.value
 
   describe 'dynamic inheritance', ->
diff --git a/spec/value_spec.moon b/spec/value_spec.moon
deleted file mode 100644
index d81ed40..0000000
--- a/spec/value_spec.moon
+++ /dev/null
@@ -1,180 +0,0 @@
-import do_setup from require 'spec.test_setup'
-import ValueStream, Result, Scope, SimpleRegistry from require 'alv'
-import Op, Builtin from require 'alv.base'
-
-class TestOp extends Op
-  new: (...) => super ...
-
-class TestBuiltin extends Builtin
-  new: (...) =>
-
-setup do_setup
-
-describe 'ValueStream', ->
-  describe '.wrap', ->
-    it 'wraps numbers', ->
-      got = ValueStream.wrap 3
-      assert.is.equal 'num', got.type
-      assert.is.equal 3, got.value
-
-    it 'wraps strings', ->
-      got = ValueStream.wrap "im a happy string"
-      assert.is.equal 'str', got.type
-      assert.is.equal "im a happy string", got.value
-
-    it 'wraps Values', ->
-      pi = ValueStream 'num', 3.14
-      got = ValueStream.wrap pi
-
-      assert.is.equal pi, got
-
-    it 'wraps Opdefs', ->
-      got = ValueStream.wrap TestOp
-
-      assert.is.equal 'opdef', got.type
-      assert.is.equal TestOp, got.value
-
-    it 'wraps Bultins', ->
-      got = ValueStream.wrap TestBuiltin
-
-      assert.is.equal 'builtin', got.type
-      assert.is.equal TestBuiltin, got.value
-
-    it 'wraps Scopes', ->
-      sub = Scope!
-      got = ValueStream.wrap sub
-
-      assert.is.equal 'scope', got.type
-      assert.is.equal sub, got.value
-
-    it 'wraps tables', ->
-      pi = ValueStream 'num', 3.14
-      got = ValueStream.wrap { :pi }
-
-      assert.is.equal 'scope', got.type
-      assert.is.equal pi, (got.value\get 'pi')\const!
-
-  describe ':unwrap', ->
-    it 'returns the raw value!', ->
-      assert.is.equal 3.14, (ValueStream.num 3.14)\unwrap!
-      assert.is.equal 'hi', (ValueStream.str 'hi')\unwrap!
-      assert.is.equal 'hi', (ValueStream.sym 'hi')\unwrap!
-
-    test 'can assert the type', ->
-      assert.is.equal 3.14, (ValueStream.num 3.14)\unwrap 'num'
-      assert.is.equal 'hi', (ValueStream.str 'hi')\unwrap 'str'
-      assert.is.equal 'hi', (ValueStream.sym 'hi')\unwrap 'sym'
-      assert.has_error -> (ValueStream.num 3.14)\unwrap 'sym'
-      assert.has_error -> (ValueStream.str 'hi')\unwrap 'num'
-      assert.has_error -> (ValueStream.sym 'hi')\unwrap 'str'
-
-    test 'has __call shorthand', ->
-      assert.is.equal 3.14, (ValueStream.num 3.14)!
-      assert.is.equal 'hi', (ValueStream.str 'hi')!
-      assert.is.equal 'hi', (ValueStream.sym 'hi')!
-      assert.is.equal 3.14, (ValueStream.num 3.14) 'num'
-      assert.is.equal 'hi', (ValueStream.str 'hi') 'str'
-      assert.is.equal 'hi', (ValueStream.sym 'hi') 'sym'
-      assert.has_error -> (ValueStream.num 3.14) 'sym'
-      assert.has_error -> (ValueStream.str 'hi') 'num'
-      assert.has_error -> (ValueStream.sym 'hi') 'str'
-
-  describe 'overrides __eq', ->
-    it 'compares the type', ->
-      val = ValueStream 'num', 3
-      assert.is.equal (ValueStream.num 3), val
-      assert.not.equal (ValueStream.str '3'), val
-
-      val = ValueStream 'str', 'hello'
-      assert.is.equal (ValueStream.str 'hello'), val
-      assert.not.equal (ValueStream.sym 'hello'), val
-
-    it 'compares the value', ->
-      val = ValueStream 'num', 3
-      assert.is.equal (ValueStream.num 3), val
-      assert.not.equal (ValueStream.num 4), val
-
-  describe ':set', ->
-    it 'sets the value', ->
-      val = ValueStream 'num', 3
-      assert.is.equal (ValueStream.num 3), val
-
-      val\set 4
-      assert.is.equal (ValueStream.num 4), val
-      assert.not.equal (ValueStream.num 3), val
-
-    it 'marks the value dirty', ->
-      val = ValueStream 'num', 3
-      assert.is.false val\dirty!
-
-      val\set 4
-      assert.is.true val\dirty!
-
-  describe ':eval', ->
-    it 'turns numbers into consts', ->
-      assert_noop = (val) ->
-        assert.is.equal val, val\eval!\const!
-
-      assert_noop ValueStream.num 2
-      assert_noop ValueStream.str 'hello'
-
-    it 'looks up symbols in the scope', ->
-      scope = with Scope!
-        \set 'number', Result value: ValueStream.num 3
-        \set 'hello', Result value: ValueStream.str "world"
-        \set 'goodbye', Result value: ValueStream.sym "again"
-
-      assert_eval = (sym, val) ->
-        const = ValueStream.sym sym
-        assert.is.equal val, (const\eval scope)\const!
-
-      assert_eval 'number', ValueStream.num 3
-      assert_eval 'hello', ValueStream.str "world"
-      assert_eval 'goodbye', ValueStream.sym "again"
-
-  it ':clone sliterals as themselves', ->
-    assert_noop = (val) -> assert.is.equal val, val\clone!
-
-    assert_noop ValueStream.num 2
-    assert_noop ValueStream.str 'hello'
-    assert_noop ValueStream.sym 'world'
-
-  describe ':fork', ->
-    it 'is equal to the original', ->
-      a = ValueStream.num 2
-      b = ValueStream.str 'asdf'
-      c = with ValueStream 'weird', {}, '(raw)'
-        \set {}
-
-      aa, bb, cc = a\fork!, b\fork!, c\fork!
-      assert.is.equal a, aa
-      assert.is.equal b, bb
-      assert.is.equal c, cc
-
-      assert.is.false aa\dirty!
-      assert.is.false bb\dirty!
-      assert.is.true cc\dirty!
-
-      assert.is.equal c.raw, cc.raw
-
-    it 'isolates the original from the fork', ->
-      a = ValueStream.num 3
-      b = with ValueStream 'weird', {}, '(raw)'
-        \set {}
-
-      aa, bb = a\fork!, b\fork!
-
-      bb\set {false}
-
-      assert.is.same {}, b!
-      assert.is.same {false}, bb!
-      assert.is.true b\dirty!
-      assert.is.true bb\dirty!
-
-      COPILOT\next_tick!
-      aa\set 4
-
-      assert.is.equal 3, a!
-      assert.is.equal 4, aa!
-      assert.is.false a\dirty!
-      assert.is.true aa\dirty!