rename RTNode.value to RTNode.result (to match Result class)

18 files changed, 170 insertions, 196 deletions

diff --git a/alv/ast.moon b/alv/ast.moon
index cff8947..b8c14e6 100644
--- a/alv/ast.moon
+++ b/alv/ast.moon
@@ -10,11 +10,11 @@
 
   --- evaluate this AST Node.
   --
-  -- Evaluate this node and return a `Result`.
+  -- Evaluate this node and return a `RTNode`.
   --
   -- @function eval
   -- @tparam Scope scope the scope to evaluate in
-  -- @treturn Result the evaluation result
+  -- @treturn RTNode the evaluation result
 
   --- create a clone with its own identity.
   --
diff --git a/alv/base/builtin.moon b/alv/base/builtin.moon
index f675207..5f46f37 100644
--- a/alv/base/builtin.moon
+++ b/alv/base/builtin.moon
@@ -31,7 +31,7 @@ class Builtin
   --
   -- @tparam Scope 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: (scope, tail) => error "not implemented"
 
   --- free resources
@@ -62,12 +62,12 @@ class Builtin
   -- Create a new instance using `tag` and `head` and call `setup` on it.
   -- If a previous instance with the same `tag` exists and has the same `head`,
   -- it pass it to `setup`. Register the `Builtin` with `tag`, evaluate it
-  -- and return the `Result`.
+  -- and return the `RTNode`.
   --
   -- @tparam Cell cell the `Cell` being evaluated
   -- @tparam Scope scope the active scope
   -- @tparam Value head the (`AST:eval`d) head of the `Cell` being evaluated
-  -- @treturn Result the result of evaluation
+  -- @treturn RTNode the result of evaluation
   @eval_cell: (cell, scope, head) =>
     last = cell.tag\last!
     compatible = last and (last.__class == @) and last.head == head
diff --git a/alv/base/input.moon b/alv/base/input.moon
index dea91c9..a9f0e32 100644
--- a/alv/base/input.moon
+++ b/alv/base/input.moon
@@ -35,7 +35,7 @@ class Input
   --- create a new Input.
   --
   -- @classmethod
-  -- @tparam Stream stream
+  -- @tparam Result stream
   new: (@stream) =>
     assert @stream, "nil passed to Input: #{value}"
 
@@ -98,26 +98,27 @@ class Input
   -- Never marked dirty. Use this for input streams that are only read when
   -- another `Input` is dirty.
   --
-  -- @tparam Stream|RTNode value
+  -- @tparam Result|RTNode value
   @cold: (value) ->
     if value.__class == RTNode
-      value = assert value.value, "Input from result without value!"
+      value = assert value.result, "Input from node without result!"
     ColdInput value
 
   --- Create a `hot` `Input`.
   --
-  -- Behaviour depends on what kind of `Stream` `value` is:
+  -- Behaviour depends on what kind of `Result` `value` is:
   --
+  -- - `Constant`: treated like `cold`.
   -- - `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|RTNode value
+  -- @tparam Result|RTNode value
   @hot: (value) ->
     if value.__class == RTNode
-      value = assert value.value, "Input from result without value!"
+      value = assert value.result, "Input from node without result!"
 
     InputType = match_parent value, mapping
     assert InputType, "Input from unknown value: #{value}"
diff --git a/alv/base/match.moon b/alv/base/match.moon
index 3a2b3d5..926c970 100644
--- a/alv/base/match.moon
+++ b/alv/base/match.moon
@@ -49,14 +49,12 @@ import Primitive from require 'alv.type'
 
 local Repeat, Sequence, Choice, Optional
 
-typestr = (result) -> tostring result.value
-
 class Pattern
   match: (seq) =>
     @reset!
     num, cap = @capture seq, 1
     if num != #seq
-      args = table.concat [typestr arg for arg in *seq], ' '
+      args = table.concat [arg.result\fulltype! for arg in *seq], ' '
       msg = "couldn't match arguments (#{args}) against pattern #{@}"
       error Error 'argument', msg
     cap
@@ -86,15 +84,15 @@ class Pattern
     cls.__base.__div or= @__div
     cls.__base.__unm or= @__unm
 
---- Base Stream Pattern.
+--- Base Result Pattern.
 --
--- When instantiated with `type`, only succeeds for `Stream`s whose value and
+-- When instantiated with `type`, only succeeds for `Result`s whose value and
 -- meta types match.
 --
 -- Otherwise, matches Streams based only on `metatype` for the first match, but
 -- using both afterwards (recall mode).
 --
--- @function Stream
+-- @function Type
 -- @tparam string metatype "value" or "event"
 -- @tparam ?string type type name
 class Type extends Pattern
diff --git a/alv/base/op.moon b/alv/base/op.moon
index b0a83dc..da90288 100644
--- a/alv/base/op.moon
+++ b/alv/base/op.moon
@@ -46,9 +46,9 @@ class Op
   --
   -- @tfield table state
 
-  --- `Stream` instance representing this Op's computed output value.
+  --- `Result` instance representing this Op's computed output value.
   --
-  -- Must be set to a `Stream` instance once `setup` finishes. Must not change
+  -- Must be set to a `Result` instance once `setup` finishes. Must not change
   -- type, be removed or replaced outside of `new` and `setup`. If it is a
   -- `ValueStream`, it should have a value assigned via `set` or the
   -- constructor once `tick` is called the first time. If `out`'s value is not
@@ -56,7 +56,7 @@ class Op
   -- `tick``(true)` is called at least on the first eval-cycle the Op goes
   -- through, e.g. by using an `Input.hot` with a `ValueStream`.
   --
-  -- @tfield Stream out
+  -- @tfield Result out
 
   --- table containing `Input`s to this Op.
   --
@@ -79,18 +79,18 @@ class Op
   --
   -- @function new
   -- @classmethod
-  -- @tparam ?Stream out `out`
+  -- @tparam ?Result out `out`
   -- @tparam ?table state `state`
 
   --- parse arguments and patch self.
   --
-  -- Called once every eval-cycle. `inputs` is a list of `Result`s that are the
+  -- Called once every eval-cycle. `inputs` is a list of `RTNode`s that are the
   -- argument to this op. The `inputs` have to be wrapped in `Input` instances
   -- to define update behaviour. Use `base.match` to parse them, then delegate to
   -- `super:setup` to patch the `Input` instances.
   --
   -- @function setup
-  -- @tparam {Result,...} inputs a sequence of `Result`s
+  -- @tparam {RTNode,...} inputs a sequence of `RTNode`s
   -- @tparam Scope scope the active scope
 
   --- handle incoming events and update `out` (optional).
@@ -120,7 +120,7 @@ class Op
   -- type is not known at this time.
   --
   -- @classmethod
-  -- @tparam ?Stream out `out`
+  -- @tparam ?Result out `out`
   -- @tparam ?table state `state`
   new: (@out, @state) =>
 
diff --git a/alv/builtin.moon b/alv/builtin.moon
index 58a1ecc..740da25 100644
--- a/alv/builtin.moon
+++ b/alv/builtin.moon
@@ -35,9 +35,9 @@ doc = Constant.meta
     eval: (scope, tail) =>
       assert #tail == 1, "'doc' takes exactly one parameter"
 
-      result = L\push tail[1]\eval, scope
+      node = L\push tail[1]\eval, scope
       with RTNode children: { def }
-        meta = result.value.meta
+        meta = node.result.meta
         L\print "(doc #{tail[1]}):\n#{format_meta meta}\n"
 
 def = Constant.meta
@@ -78,8 +78,8 @@ All arguments have to be evaltime constant."
     eval: (scope, tail) =>
       L\trace "evaling #{@}"
       for child in *tail
-        result = L\push child\eval, scope
-        value = result\const!
+        node = L\push child\eval, scope
+        value = node\const!
         scope\use value\unwrap 'scope', "'use' only works on scopes"
 
       RTNode!
@@ -96,8 +96,8 @@ require_ = Constant.meta
       L\trace "evaling #{@}"
       assert #tail == 1, "'require' takes exactly one parameter"
 
-      result = L\push tail[1]\eval, scope
-      name = result\const!\unwrap 'str'
+      node = L\push tail[1]\eval, scope
+      name = node\const!\unwrap 'str'
 
       L\trace @, "loading module #{name}"
       COPILOT\require name
@@ -148,11 +148,11 @@ export_ = Constant.meta
     description: "
 Evaluate `expr1`, `expr2`, … in a new Scope and return scope."
 
-  value: class  extends Builtin
+  value: class extends Builtin
     eval: (scope, tail) =>
       new_scope = Scope scope
       children = [expr\eval new_scope for expr in *tail]
-      RTNode :children, value: Constant.wrap new_scope
+      RTNode :children, result: Constant.wrap new_scope
 
 export_star = Constant.meta
   meta:
@@ -170,16 +170,16 @@ Copies the containing scope if no symbols are given."
       new_scope = Scope!
 
       children = if #tail == 0
-        for k,result in pairs scope.values
-          new_scope\set k, result
-          result
+        for k,node in pairs scope.values
+          new_scope\set k, node
+          node
       else
         for child in *tail
           name = child\unwrap 'sym'
-          with result = scope\get name
-            new_scope\set name, result
+          with node = scope\get name
+            new_scope\set name, node
 
-      RTNode :children, value: Constant.wrap new_scope
+      RTNode :children, result: Constant.wrap new_scope
 
 fn = Constant.meta
   meta:
@@ -201,7 +201,7 @@ function is invoked."
         assert param.type == 'sym', "function parameter declaration has to be a symbol"
         param
 
-      RTNode value: with Constant.wrap FnDef param_symbols, body, scope
+      RTNode result: with Constant.wrap FnDef param_symbols, body, scope
         .meta = {
           summary: "(user defined function)"
           examples: { "(??? #{table.concat [p! for p in *param_symbols], ' '})" }
@@ -229,13 +229,13 @@ function is invoked."
         assert param.type == 'sym', "function parameter declaration has to be a symbol"
         param
 
-      value = with Constant.wrap FnDef param_symbols, body, scope
+      result = 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, RTNode :value
+      scope\set name, RTNode :result
       RTNode!
 
 do_expr = Constant.meta
@@ -246,11 +246,11 @@ do_expr = Constant.meta
     description: "
 Evaluate `expr1`, `expr2`, … and return the value of the last expression."
 
-  value: class  extends Builtin
+  value: class extends Builtin
     eval: (scope, tail) =>
       scope = Scope scope
       children = [expr\eval scope for expr in *tail]
-      RTNode :children, value: children[#children].value
+      RTNode :children, result: children[#children].result
 
 if_ = Constant.meta
   meta:
@@ -288,8 +288,8 @@ trace_ = Constant.meta
       L\trace "evaling #{@}"
       assert #tail == 1, "'trace!' takes exactly one parameter"
 
-      with result = L\push tail[1]\eval, scope
-        L\print "trace! #{tail[1]\stringify!}: #{result.value}"
+      with node = L\push tail[1]\eval, scope
+        L\print "trace! #{tail[1]\stringify!}: #{node.result}"
 
 trace = Constant.meta
   meta:
diff --git a/alv/cell.moon b/alv/cell.moon
index 933d292..a61f8de 100644
--- a/alv/cell.moon
+++ b/alv/cell.moon
@@ -69,7 +69,7 @@ class Cell
   -- then calls `Builtin:eval_cell` on it.
   --
   -- @tparam Scope scope the scope to evaluate in
-  -- @treturn Result the evaluation result
+  -- @treturn RTNode the evaluation result
   eval: (scope) =>
     head = assert @head!, Error 'syntax', "cannot evaluate empty expr"
     head = (head\eval scope)\const!
diff --git a/alv/copilot.moon b/alv/copilot.moon
index d9b674f..55e00c8 100644
--- a/alv/copilot.moon
+++ b/alv/copilot.moon
@@ -46,7 +46,7 @@ class Copilot
     Error.wrap "loading module '#{name}'", ->
       ok, lua = pcall require, "alv-lib.#{name}"
       if ok
-        RTNode value: Constant.wrap lua
+        RTNode result: Constant.wrap lua
       else
         assert @modules, "no current eval cycle?"
         if mod = @modules[name]
diff --git a/alv/invoke.moon b/alv/invoke.moon
index 03cf08e..0629b59 100644
--- a/alv/invoke.moon
+++ b/alv/invoke.moon
@@ -64,7 +64,7 @@ class op_invoke extends Builtin
     children = [L\push expr\eval, scope for expr in *tail]
 
     frame = "invoking op #{get_name @head, @cell\head!} at [#{@tag}]"
-    Error.wrap frame, @op\setup, [result for result in *children], scope
+    Error.wrap frame, @op\setup, [node for node in *children], scope
 
     any_dirty = false
     for input in @op\all_inputs!
@@ -78,7 +78,7 @@ class op_invoke extends Builtin
     for input in @op\all_inputs!
       input\finish_setup!
 
-    RTNode :children, value: @op.out, op: @op
+    RTNode :children, result: @op.out, op: @op
 
   --- The `Op` instance.
   --
@@ -123,10 +123,10 @@ class fn_invoke extends Builtin
         fn_scope\set name, \make_ref!
 
     clone = body\clone @tag
-    result = Error.wrap frame, clone\eval, fn_scope
+    node = Error.wrap frame, clone\eval, fn_scope
 
-    table.insert children, result
-    RTNode :children, value: result.value
+    table.insert children, node
+    RTNode :children, result: node.result
 
 {
   :op_invoke, :fn_invoke
diff --git a/alv/module.moon b/alv/module.moon
index 8fc3ba7..7179ab6 100644
--- a/alv/module.moon
+++ b/alv/module.moon
@@ -67,8 +67,8 @@ class Module
   --- the last updated AST tree for this module.
   -- @tfield ?AST ast
 
-  --- the root Result of this module.
-  -- @tfield ?Result root
+  --- the runtime graph root of this module.
+  -- @tfield ?RTNode root
 
 {
   :Module
diff --git a/alv/registry.moon b/alv/registry.moon
index 1b24e9a..0d37a5c 100644
--- a/alv/registry.moon
+++ b/alv/registry.moon
@@ -2,8 +2,6 @@
 -- `Tag` Registry.
 --
 -- @classmod Registry
-import Result from require 'alv.result'
-import Error from require 'alv.error'
 
 class Registry
 --- internals for `Tag`
diff --git a/alv/result/base.moon b/alv/result/base.moon
index 26af4b4..bbbbeac 100644
--- a/alv/result/base.moon
+++ b/alv/result/base.moon
@@ -1,55 +1,45 @@
 ----
--- base Stream interface.
+-- base Result interface.
 --
 -- implemented by `Constant`, `SigStream`, `EvtStream`, and `IOStream`.
 --
--- @classmod Stream
+-- @classmod Result
 
-class Stream
---- Stream interface.
+class Result
+--- Result interface.
 --
--- Methods that have to be implemented by `Stream` implementations
+-- Methods that have to be implemented by `Result` implementations
 -- (`SigStream`, `EvtStream`, `IOStream`).
 --
 -- @section interface
 
-  --- return whether this Stream was changed in the current tick.
-  --
+  --- return whether this Result was changed in the current tick.
   -- @function dirty
   -- @treturn boolean
 
-  --- create a mutable copy of this Stream.
+  --- create a mutable copy of this Result.
   --
   -- Used to insulate eval-cycles from each other.
   --
   -- @function fork
-  -- @treturn Stream
+  -- @treturn Result
 
   __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:
-  --
-  -- - `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
-  --
+  --- the type name of this Result's value.
   -- @tfield string type
 
-  --- the metatype string for this Stream.
+  --- the metatype string for this Result.
   --
   -- one of `=` (`Constant`), `~` (`SigStream`),
   -- `!` (`EvtStream` and `IOStream`).
   --
-  -- @tfield string type
+  -- @tfield string metatype
+
+  --- get the full typestring.
+  -- @treturn string `type .. metatype`
+  fulltype: => (tostring @type) .. @metatype
 
   --- documentation metadata.
   --
@@ -66,7 +56,7 @@ class Stream
 --- static functions
 -- @section static
 
-  --- construct a new Stream.
+  --- construct a new Result.
   --
   -- @classmethod
   -- @tparam string type the type name
@@ -74,5 +64,5 @@ class Stream
   new: (@type, @meta={}) =>
 
 {
-  :Stream
+  :Result
 }
diff --git a/alv/result/const.moon b/alv/result/const.moon
index b9a7cf4..615e426 100644
--- a/alv/result/const.moon
+++ b/alv/result/const.moon
@@ -1,10 +1,10 @@
 ----
 -- Constant Value.
 --
--- Implements the `Stream` and `AST` inteface.
+-- Implements the `Result` and `AST` inteface.
 --
 -- @classmod Constant
-import Stream from require 'alv.result.base'
+import Result from require 'alv.result.base'
 import Primitive from require 'alv.type'
 import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
@@ -21,10 +21,14 @@ ancestor = (klass) ->
     klass = klass.__parent
   klass
 
-class Constant extends Stream
-  --- Whether this Result is dirty.
-  --
-  -- @treturn bool always `false`.
+class Constant extends Result
+--- Result interface
+--
+-- `Constant` implements the `Result` interface.
+-- @section result
+
+  --- return whether this Result was changed in the current tick.
+  -- @treturn bool
   dirty: => false
 
   --- unwrap to the Lua type.
@@ -53,14 +57,13 @@ class Constant extends Stream
   -- Compares two `SigStream`s by comparing their types and their Lua values.
   __eq: (other) => other.type == @type and other.value == @value
 
-  --- Stream metatype.
-  --
+  --- Result metatype.
   -- @tfield string metatype (`=`)
   metatype: '='
 
 --- AST interface
 --
--- `SignStream` implements the `AST` interface.
+-- `Constant` implements the `AST` interface.
 -- @section ast
 
   --- evaluate this literal constant.
@@ -72,11 +75,11 @@ class Constant extends Stream
   -- @tparam Scope scope the scope to evaluate in
   -- @treturn RTNode the evaluation result
   eval: (scope) =>
-    return RTNode value: @ if @literal
+    return RTNode result: @ if @literal
 
     switch @type
       when num, str
-        RTNode value: @
+        RTNode result: @
       when sym
         Error.wrap "resolving symbol '#{@value}'", scope\get, @value
       else
@@ -140,7 +143,7 @@ class Constant extends Stream
           switch ancestor val.__class
             when scope.Scope then 'scope'
             when base.FnDef then 'fndef'
-            when Stream then return val
+            when Result then return val
             else
               error "#{name}: cannot wrap '#{val.__class.__name}' instance"
         else
diff --git a/alv/result/evt.moon b/alv/result/evt.moon
index 0559a70..fdec85e 100644
--- a/alv/result/evt.moon
+++ b/alv/result/evt.moon
@@ -2,29 +2,18 @@
 -- Stream of momentary events.
 --
 -- @classmod EvtStream
-import Stream from require 'alv.result.base'
+import Result from require 'alv.result.base'
 
-class EvtStream extends Stream
---- members
--- @section members
+class EvtStream extends Result
+--- Result interface
+--
+-- `EvtStream` implements the `Result` interface.
+-- @section result
 
-  --- return whether this stream was changed in the current tick.
-  --
+  --- return whether this Result was changed in the current tick.
   -- @treturn bool
   dirty: => @updated == COPILOT.T
 
-  --- push an event value into the stream.
-  --
-  -- Marks this stream as dirty for the remainder of the current tick.
-  --
-  -- @tparam any event
-  add: (event) =>
-    if not @dirty!
-      @events = {}
-
-    @updated = COPILOT.T
-    table.insert @events, event
-
   --- get the sequence of current events (if any).
   --
   -- Returns `events` if `dirty`, or an empty table otherwise.
@@ -48,27 +37,13 @@ class EvtStream extends Stream
   __call: (...) => @unwrap ...
   __tostring: => "<#{@type}#{@metatype} #{@type\pp @value}>"
 
-  --- Stream metatype.
-  --
+  --- the type name of this Result's value.
+  -- @tfield string type
+
+  --- the metatype string for this Result.
   -- @tfield string metatype (`!`)
   metatype: '!'
 
-  --- the type name of the 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
-
   --- documentation metadata.
   --
   -- an optional table containing metadata for error messages and
@@ -81,6 +56,22 @@ class EvtStream extends Stream
   --
   -- @tfield ?table meta
 
+--- members
+-- @section members
+
+  --- push an event value into the stream.
+  --
+  -- Marks this stream as dirty for the remainder of the current tick.
+  --
+  -- @tparam any event
+  add: (event) =>
+    if not @dirty!
+      @events = {}
+
+    @updated = COPILOT.T
+    table.insert @events, event
+
+
 --- static functions
 -- @section static
 
diff --git a/alv/result/init.moon b/alv/result/init.moon
index aa7a115..200e4e1 100644
--- a/alv/result/init.moon
+++ b/alv/result/init.moon
@@ -1,13 +1,13 @@
 ----
--- `Stream` interface and implementations.
+-- `Result` interface and implementations.
 --
--- @see Stream
+-- @see Result
 -- @see Constant
 -- @see SigStream
 -- @see EvtStream
 -- @see IOStream
 --
--- @module stream
+-- @module result
 import Constant from require 'alv.result.const'
 import SigStream from require 'alv.result.sig'
 import EvtStream from require 'alv.result.evt'
diff --git a/alv/result/sig.moon b/alv/result/sig.moon
index 6bcba65..8ca59b7 100644
--- a/alv/result/sig.moon
+++ b/alv/result/sig.moon
@@ -2,26 +2,19 @@
 -- Continuous stream of values.
 --
 -- @classmod SigStream
-import Stream from require 'alv.result.base'
+import Result from require 'alv.result.base'
 import Primitive from require 'alv.type'
 
-class SigStream extends Stream
---- members
--- @section members
+class SigStream extends Result
+--- Result interface
+--
+-- `SigStream` implements the `Result` interface.
+-- @section result
 
-  --- return whether this stream was changed in the current tick.
-  --
+  --- return whether this Result 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.
@@ -50,29 +43,12 @@ class SigStream extends Stream
   -- 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
-  --
+  --- the type name of this Result's value.
   -- @tfield string type
 
-  --- the wrapped Lua value.
-  -- @tfield any value
+  --- the metatype string for this Result.
+  -- @tfield string metatype (`~`)
+  metatype: '~'
 
   --- documentation metadata.
   --
@@ -86,6 +62,20 @@ class SigStream extends Stream
   --
   -- @tfield ?table meta
 
+--- members
+-- @section members
+
+  --- 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
+
+  --- the wrapped Lua value.
+  -- @tfield any value
+
 --- static functions
 -- @section static
 
diff --git a/alv/rtnode.moon b/alv/rtnode.moon
index dab4507..a8ebec3 100644
--- a/alv/rtnode.moon
+++ b/alv/rtnode.moon
@@ -9,33 +9,33 @@ class RTNode
 --- members
 -- @section members
 
-  --- return whether this RTNode's value is const.
+  --- return whether this RTNode's result is const.
   is_const: => not next @side_inputs
 
-  --- assert value-constness and return the value.
+  --- assert result-constness and return the result.
   -- @tparam[opt] string msg the error message to throw
   -- @treturn any
   const: (msg) =>
     assert not (next @side_inputs), msg or "eval-time const expected"
-    @value
+    @result
 
-  --- assert this result has a value, return its type.
+  --- assert this result has a result, return its type.
   -- @treturn string
   type: =>
-    assert @value, "RTNode with value expected"
-    @value.type
+    assert @result, "RTNode with result expected"
+    @result.type
 
-  --- assert this result has a value, returns its metatype.
-  -- @treturn string `"value"` or `"event"`
+  --- assert this result has a result, returns its metatype.
+  -- @treturn string `"result"` or `"event"`
   metatype: =>
-    assert @value, "RTNode with value expected"
-    @value.metatype
+    assert @result, "RTNode with result expected"
+    @result.metatype
 
-  --- create a copy of this result with value-copy semantics.
-  -- the copy has the same @value and @side_inputs, but will not update
+  --- create a copy of this result with result-copy semantics.
+  -- the copy has the same @result and @side_inputs, but will not update
   -- anything on \tick.
   make_ref: =>
-    with RTNode value: @value
+    with RTNode result: @result
       .side_inputs = @side_inputs
 
   --- poll all IOStream instances that are effecting this (sub)tree.
@@ -73,15 +73,15 @@ class RTNode
       @op\tick!
 
   __tostring: =>
-    buf = "<RT=#{@value}"
+    buf = "<RT=#{@result}"
     buf ..= " #{@op}" if @op
     buf ..= " (#{#@children} children)" if #@children > 0
     buf ..= ">"
     buf
 
-  --- the `Stream` result
+  --- the `Result` result
   --
-  -- @tfield ?Stream value
+  -- @tfield ?Result result
 
   --- an Op
   --
@@ -91,21 +91,21 @@ class RTNode
   --
   -- @tfield {}|{RTNode,...} children
 
-  --- cached mapping of all `Stream`/`Input` pairs affecting this RTNode.
+  --- cached mapping of all `Result`/`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.
+  -- `op` that are not the `result` of any child.
   --
-  -- @tfield {[Stream]=Input,...} side_inputs
+  -- @tfield {[Result]=Input,...} side_inputs
 
 --- static functions
 -- @section static
 
   --- create a new RTNode.
   -- @classmethod
-  -- @param params table with optional keys op, value, children. default: {}
+  -- @param params table with optional keys op, result, children. default: {}
   new: (params={}) =>
-    @value = params.value
+    @result = params.result
     @op = params.op
     @children = params.children or {}
 
@@ -113,14 +113,17 @@ class RTNode
     for child in *@children
       for stream, input in pairs child.side_inputs
         @side_inputs[stream] = input
-      if child.value
-        is_child[child.value] = true
+      if child.result
+        is_child[child.result] = true
 
     if @op
       for input in @op\all_inputs!
         if input.io or not is_child[input.stream]
           @side_inputs[input.stream] = input
 
+    if @result and @result.metatype == '='
+      assert not (next @side_inputs), "Const result has side_inputs"
+
 {
   :RTNode
 }
diff --git a/alv/scope.moon b/alv/scope.moon
index c2c91e1..462d7a6 100644
--- a/alv/scope.moon
+++ b/alv/scope.moon
@@ -18,8 +18,8 @@ class Scope
   -- @tparam string key
   -- @tparam any val
   set_raw: (key, val) =>
-    value = Constant.wrap val, key
-    @values[key] = RTNode :value
+    result = Constant.wrap val, key
+    @values[key] = RTNode :result
 
   --- set a symbol to a `RTNode`.
   --
@@ -28,7 +28,7 @@ class Scope
   set: (key, val) =>
     L\trace "setting #{key} = #{val} in #{@}"
     assert val.__class == RTNode, "expected #{key}=#{val} to be RTNode"
-    assert val.value, Error 'type', "cannot define symbol to nil"
+    assert val.result, Error 'type', "cannot define symbol to nil"
     assert not @values[key], Error 'type', "cannot redefine symbol '#{key}'!"
     @values[key] = val
 
@@ -59,7 +59,7 @@ class Scope
       error Error 'reference', "undefined symbol '#{start}'"
     if child\type! != (Primitive 'scope')
       error Error 'reference', "'#{start}' is not a scope"
-    child.value!\get rest, while_msg
+    child.result!\get rest, while_msg
 
   --- copy definitions from another scope.
   --