add types.T, fix spec + docs

16 files changed, 159 insertions, 168 deletions

diff --git a/alv/base/init.moon b/alv/base/init.moon
index 62de2ab..90f1dfc 100644
--- a/alv/base/init.moon
+++ b/alv/base/init.moon
@@ -15,6 +15,10 @@
 -- @see SigStream
 -- @see EvtStream
 -- @see IOStream
+-- @see type.T
+-- @see type.Primitive
+-- @see type.Array
+-- @see type.Struct
 -- @see RTNode
 -- @see Error
 
@@ -24,7 +28,7 @@ import FnDef from require 'alv.base.fndef'
 import Input from require 'alv.base.input'
 import val, evt from require 'alv.base.match'
 import Constant, SigStream, EvtStream, IOStream from require 'alv.result'
-import Primitive, Array, Struct from require 'alv.type'
+import T, Primitive, Array, Struct from require 'alv.type'
 import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
 
@@ -41,7 +45,7 @@ import Error from require 'alv.error'
   :Constant, :SigStream, :EvtStream, :IOStream
 
   -- Types
-  :Primitive, :Array, :Struct
+  :T, :Primitive, :Array, :Struct
 
   :RTNode
   :Error
diff --git a/alv/base/input.moon b/alv/base/input.moon
index a9f0e32..b73a476 100644
--- a/alv/base/input.moon
+++ b/alv/base/input.moon
@@ -35,9 +35,9 @@ class Input
   --- create a new Input.
   --
   -- @classmethod
-  -- @tparam Result stream
-  new: (@stream) =>
-    assert @stream, "nil passed to Input: #{value}"
+  -- @tparam Result result
+  new: (@result) =>
+    assert @result, "nil passed to Input: #{value}"
 
   --- copy state from old instance (optional).
   --
@@ -53,10 +53,10 @@ 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`:@{SigStream:dirty|dirty}.
+  -- `result`:@{SigStream:dirty|dirty}.
   --
   -- @treturn bool whether processing is necessary
-  dirty: => @stream\dirty!
+  dirty: => @result\dirty!
 
   --- leave setup state (optional).
   --
@@ -67,25 +67,25 @@ class Input
   --- unwrap to Lua value (optional).
   --
   -- @treturn any the raw Lua value
-  unwrap: => @stream\unwrap!
+  unwrap: => @result\unwrap!
 
   --- return the type name of this `Input` (optional).
-  type: => @stream.type
+  type: => @result.type
 
   --- return the metatype name of this `Input` (optional).
-  metatype: => @stream.metatype
+  metatype: => @result.metatype
 
   --- the current value
   --
-  -- @tfield SigStream stream
+  -- @tfield SigStream result
 
 --- members
 -- @section members
 
   --- alias for `unwrap`.
-  __call: => @stream\unwrap!
+  __call: => @result\unwrap!
 
-  __tostring: => "#{@@__name}:#{@stream}"
+  __tostring: => "#{@@__name}:#{@result}"
   __inherited: (cls) =>
     cls.__base.__call = @__call
     cls.__base.__tostring = @__tostring
@@ -95,7 +95,7 @@ class Input
 
   --- Create a `cold` `Input`.
   --
-  -- Never marked dirty. Use this for input streams that are only read when
+  -- Never marked dirty. Use this for input results that are only read when
   -- another `Input` is dirty.
   --
   -- @tparam Result|RTNode value
@@ -128,17 +128,17 @@ class ColdInput extends Input
   dirty: => false
 
 class ValueInput extends Input
-  setup: (old) => @dirty_setup = not old or @stream != old.stream
+  setup: (old) => @dirty_setup = not old or @result != old.result
   finish_setup: => @dirty_setup = nil
   dirty: =>
     return @dirty_setup if @dirty_setup != nil
-    @stream\dirty!
+    @result\dirty!
 
 class IOInput extends Input
   io: true
 
 mapping = {
-  [Constant]: ColdInput
+  [Constant]: ValueInput
   [SigStream]: ValueInput
   [EvtStream]: Input
   [IOStream]: IOInput
diff --git a/alv/builtin.moon b/alv/builtin.moon
index 29602e2..45ee626 100644
--- a/alv/builtin.moon
+++ b/alv/builtin.moon
@@ -5,7 +5,7 @@
 -- documentation.
 --
 -- @module builtin
-import Builtin, Op, Primitive, FnDef, Input, val, evt from require 'alv.base'
+import Builtin, Op, T, FnDef, Input, val, evt from require 'alv.base'
 import Constant from require 'alv.result'
 import Error from require 'alv.error'
 import RTNode from require 'alv.rtnode'
@@ -58,7 +58,7 @@ Define the symbols `sym1`, `sym2`, … to resolve to the values of `val-expr1`,
       children = L\push ->
         return for i=1,#tail,2
           name, val_expr = tail[i], tail[i+1]
-          name = name\unwrap 'sym'
+          name = name\unwrap T.sym
 
           with val_expr\eval scope
             scope\set name, \make_ref!
@@ -117,7 +117,7 @@ current scope."
       assert #tail > 0, "'import' requires at least one arguments"
 
       children = for i, child in ipairs tail
-        name = child\unwrap 'sym'
+        name = child\unwrap T.sym
         with COPILOT\require name
           scope\set name, \make_ref!
       RTNode :children
@@ -136,8 +136,8 @@ Requires modules `sym1`, `sym2`, … and merges them into the current scope."
       assert #tail > 0, "'import' requires at least one arguments"
 
       children = for i, child in ipairs tail
-        with COPILOT\require child\unwrap 'sym'
-          scope\use .value\unwrap 'scope'
+        with COPILOT\require child\unwrap T.sym
+          scope\use .result\unwrap T.scope
       RTNode :children
 
 export_ = Constant.meta
@@ -175,7 +175,7 @@ Copies the containing scope if no symbols are given."
           node
       else
         for child in *tail
-          name = child\unwrap 'sym'
+          name = child\unwrap T.sym
           with node = scope\get name
             new_scope\set name, node
 
@@ -198,7 +198,7 @@ function is invoked."
 
       assert params.__class == Cell, "'fn's first argument has to be an expression"
       param_symbols = for param in *params.children
-        assert param.type == 'sym', "function parameter declaration has to be a symbol"
+        assert param.type == T.sym, "function parameter declaration has to be a symbol"
         param
 
       RTNode result: with Constant.wrap FnDef param_symbols, body, scope
@@ -223,10 +223,10 @@ function is invoked."
       assert #tail == 3, "'defn' takes exactly three arguments"
       { name, params, body } = tail
 
-      name = name\unwrap 'sym'
+      name = name\unwrap T.sym
       assert params.__class == Cell, "'defn's second argument has to be an expression"
       param_symbols = for param in *params.children
-        assert param.type == 'sym', "function parameter declaration has to be a symbol"
+        assert param.type == T.sym, "function parameter declaration has to be a symbol"
         param
 
       result = with Constant.wrap FnDef param_symbols, body, scope
@@ -305,7 +305,7 @@ trace = Constant.meta
           value: Input.hot inputs[2]
 
       tick: =>
-        L\print "trace #{@inputs.prefix!}: #{@inputs.value.stream}"
+        L\print "trace #{@inputs.prefix!}: #{@inputs.value\type!\pp @inputs.value!}"
 
     eval: (scope, tail) =>
       L\trace "evaling #{@}"
@@ -313,7 +313,7 @@ trace = Constant.meta
 
       tag = @tag\clone Tag.parse '-1'
       inner = Cell tag, {
-        Constant.literal Primitive.op, traceOp, 'trace'
+        Constant.literal T.opdef, traceOp, 'trace'
         Constant.str tostring tail[1]
         tail[1]
       }
@@ -364,7 +364,7 @@ Scope.from_table {
     meta:
       name: 'bang'
       summary: "A `bang` value-constant."
-    value: Constant 'bang', true
+    value: Constant T.bang, true
 
   :fn, :defn
   'do': do_expr
diff --git a/alv/cell.moon b/alv/cell.moon
index 759e7aa..36d5f43 100644
--- a/alv/cell.moon
+++ b/alv/cell.moon
@@ -5,7 +5,7 @@
 -- nodes), a `Tag`, and optionally the internal whitespace as parsed.
 --
 -- @classmod Cell
-import Primitive from require 'alv.type'
+import T from require 'alv.type'
 import Constant from require 'alv.result'
 import Error from require 'alv.error'
 import op_invoke, fn_invoke from require 'alv.invoke'
@@ -74,11 +74,11 @@ class Cell
     head = assert @head!, Error 'syntax', "cannot evaluate empty expr"
     head = (head\eval scope)\const!
     Builtin = switch head.type
-      when Primitive.op
+      when T.opdef
         op_invoke
-      when Primitive.fn
+      when T.fndef
         fn_invoke
-      when Primitive.builtin
+      when T.builtin
         head\unwrap!
       else
         error Error 'type', "#{head} is not an opdef, fndef or builtin"
diff --git a/alv/copilot.moon b/alv/copilot.moon
index 55e00c8..e6eb293 100644
--- a/alv/copilot.moon
+++ b/alv/copilot.moon
@@ -53,7 +53,7 @@ class Copilot
           mod.root\make_ref!
         else
           last = @active_module
-          prefix = @active_module.file\match('(.*)/[^/]*$') .. '/' or ''
+          prefix = if b = last.file\match'(.*)/[^/]*$' then b .. '/' else ''
           mod = @last_modules[name] or Module "#{prefix}#{name}.alv"
           L\trace "entering module #{mod}"
           @modules[name] = mod
diff --git a/alv/error.moon b/alv/error.moon
index e72cc5f..c049f8f 100644
--- a/alv/error.moon
+++ b/alv/error.moon
@@ -48,7 +48,9 @@ class Error
     if err.__class == Error
       err
     else
-      Error 'implementation', err, debug.traceback "Lua error below:", 2
+      trace = debug.traceback "Lua error below:", 2
+      Error 'implementation', err, trace
+
   --- Wrap function errors in a traceback frame.
   --
   -- Execute `fn(...)`, and turn any error thrown as a result into an
@@ -65,8 +67,8 @@ class Error
     if ok
       unpack results
     else
-      error with results[1]
-        \add_frame frame
+      results[1]\add_frame frame if frame
+      error results[1]
 
   --- Capture and wrap function errors in traceback frame.
   --
@@ -76,7 +78,7 @@ class Error
   -- When `Error` instances are caught, `frame` is added to the traceback.
   -- All other error values are turned into `'implementation'` Errors.
   --
-  -- @tparam string frame
+  -- @tparam ?string frame
   -- @tparam function fn
   -- @treturn boolean `ok` true if exeuction suceeded without errors
   -- @treturn Error|any `error_or_results` the `Error` instance or results
@@ -86,9 +88,8 @@ class Error
     if ok
       ok, unpack results
     else
-      ok, with results[1]
-        \add_frame frame
-
+      results[1]\add_frame frame if frame
+      ok, unpack results
 {
   :Error
 }
diff --git a/alv/init.moon b/alv/init.moon
index ec90a10..fc85f8b 100644
--- a/alv/init.moon
+++ b/alv/init.moon
@@ -14,7 +14,7 @@ cycle = require 'alv.cycle'
 version = require 'alv.version'
 import Logger from require 'alv.logger'
 
-import Primitive, Struct, Array from require 'alv.type'
+import T, Primitive, Struct, Array from require 'alv.type'
 import Constant, SigStream, EvtStream, IOStream from require 'alv.result'
 import RTNode from require 'alv.rtnode'
 import Scope from require 'alv.scope'
@@ -40,6 +40,10 @@ import Copilot from require 'alv.copilot'
 -- @tfield SigStream SigStream
 -- @tfield EvtStream EvtStream
 -- @tfield IOStream IOStream
+-- @tfield type.T T
+-- @tfield type.Primitive Primitive
+-- @tfield type.Array Array
+-- @tfield type.Struct Struct
 -- @tfield RTNode RTNode
 -- @tfield Cell Cell
 -- @tfield RootCell RootCell
@@ -58,7 +62,7 @@ import Copilot from require 'alv.copilot'
   :Cell, :RootCell
   :RTNode, :Scope, :Error
 
-  :Primitive, :Struct, :Array
+  :T, :Primitive, :Struct, :Array
 
   :Registry, :SimpleRegistry, :Tag
 
diff --git a/alv/invoke.moon b/alv/invoke.moon
index 390e19f..9acb77c 100644
--- a/alv/invoke.moon
+++ b/alv/invoke.moon
@@ -5,7 +5,7 @@
 import RTNode from require 'alv.rtnode'
 import Builtin from require 'alv.base'
 import Scope from require 'alv.scope'
-import Primitive from require 'alv.type'
+import T from require 'alv.type'
 import Error from require 'alv.error'
 
 get_name = (value, raw) ->
@@ -35,14 +35,14 @@ class op_invoke extends Builtin
       @op = prev.op\fork!
       prev.forked = COPILOT.T
     else
-      def = @head\unwrap Primitive.opdef, "cant op-invoke #{@head}"
+      def = @head\unwrap T.opdef, "cant op-invoke #{@head}"
       @op = def!
 
   --- `Builtin:destroy` implementation.
   --
   -- calls `op`:@{Op:destroy|destroy}.
   destroy: =>
-    if @forked ~= COPILOT.T
+    if @op and @forked ~= COPILOT.T
       @op\destroy!
 
   --- perform an `Op` invocation.
@@ -60,19 +60,20 @@ 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, [node for node in *children], scope
+    Error.wrap frame, ->
+      @op\setup [node for node in *children], scope
 
-    any_dirty = false
-    for input in @op\all_inputs!
-      if input\dirty!
-        any_dirty = true
-        break
+      any_dirty = false
+      for input in @op\all_inputs!
+        if input\dirty!
+          any_dirty = true
+          break
 
-    if any_dirty
-      @op\tick true
+      if any_dirty
+        @op\tick true
 
-    for input in @op\all_inputs!
-      input\finish_setup!
+      for input in @op\all_inputs!
+        input\finish_setup!
 
     RTNode :children, result: @op.out, op: @op
 
@@ -104,7 +105,7 @@ class fn_invoke extends Builtin
     name = get_name @head, @cell\head!
     frame = "invoking function #{name} at [#{@tag}]"
 
-    fndef = @head\unwrap Primitive.fndef, "cant fn-invoke #{@head}"
+    fndef = @head\unwrap T.fndef, "cant fn-invoke #{@head}"
     { :params, :body } = fndef
     if #params != #tail
       err = Error 'argument', "expected #{#params} arguments, found #{#tail}"
@@ -114,7 +115,7 @@ class fn_invoke extends Builtin
     fn_scope = Scope fndef.scope, caller_scope
 
     children = for i=1,#params
-      name = params[i]\unwrap Primitive.sym
+      name = params[i]\unwrap T.sym
       with L\push tail[i]\eval, caller_scope
         fn_scope\set name, \make_ref!
 
diff --git a/alv/module.moon b/alv/module.moon
index 7179ab6..0e95593 100644
--- a/alv/module.moon
+++ b/alv/module.moon
@@ -34,7 +34,7 @@ class Module
   -- @treturn bool whether the file was changed since the last call
   poll: =>
     { :mode, :modification } = (lfs.attributes @file) or {}
-    assert mode == 'file', Error 'io', "not a file: '#{file}'"
+    assert mode == 'file', Error 'io', "not a file: '#{@file}'"
     modification
 
   --- start an evaluation cycle.
diff --git a/alv/result/base.moon b/alv/result/base.moon
index 6accb1e..7775349 100644
--- a/alv/result/base.moon
+++ b/alv/result/base.moon
@@ -24,7 +24,11 @@ class Result
   -- @function fork
   -- @treturn Result
 
-  __tostring: => "<#{@type}#{@metatype} #{@type\pp @value}>"
+  __tostring: =>
+    if @value then
+      "<#{@type}#{@metatype} #{@type\pp @value}>"
+    else
+      "<#{@type}#{@metatype}>"
   __inherited: (cls) => cls.__base.__tostring or= @__tostring
 
   --- the type of this Result's value.
@@ -56,12 +60,14 @@ class Result
 --- static functions
 -- @section static
 
+  _type = type
   --- construct a new Result.
   --
   -- @classmethod
   -- @tparam type.Type type the type
   -- @tparam ?table meta the `meta` table
   new: (@type, @meta={}) =>
+    assert @type and (_type @type) == 'table', "not a type: #{@type}"
 
 {
   :Result
diff --git a/alv/result/const.moon b/alv/result/const.moon
index b88de2c..077a2d8 100644
--- a/alv/result/const.moon
+++ b/alv/result/const.moon
@@ -5,16 +5,11 @@
 --
 -- @classmod Constant
 import Result from require 'alv.result.base'
-import Primitive from require 'alv.type'
+import T from require 'alv.type'
 import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
 import scope, base from require 'alv.cycle'
 
-num = Primitive 'num'
-str = Primitive 'str'
-sym = Primitive 'sym'
-bool = Primitive 'bool'
-
 ancestor = (klass) ->
   assert klass, "cant find the ancestor of nil"
   while klass.__parent
@@ -78,9 +73,9 @@ class Constant extends Result
     return RTNode result: @ if @literal
 
     switch @type
-      when num, str
+      when T.num, T.str
         RTNode result: @
-      when sym
+      when T.sym
         Error.wrap "resolving symbol '#{@value}'", scope\get, @value
       else
         error "cannot evaluate #{@}"
@@ -106,7 +101,9 @@ class Constant extends Result
   -- @tparam string type the type name
   -- @tparam any value the Lua value to be accessed through `unwrap`
   -- @tparam string raw the raw string that resulted in this value. Used by `parsing`.
-  new: (type, @value, @raw) => super type
+  new: (type, @value, @raw) =>
+    super type
+    assert @value ~= nil, "Constant without value"
 
   unescape = (str) -> str\gsub '\\([\'"\\])', '%1'
   --- create a capture-function (for parsing with Lpeg).
@@ -115,9 +112,9 @@ class Constant extends Result
   -- @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) -> @ T.num, (tonumber match), match
+      when 'sym' then (match) -> @ T.sym, match, match
+      when 'str' then (match) -> @ T.str, (unescape match), sep .. match .. sep
 
   --- wrap a Lua value.
   --
@@ -128,28 +125,28 @@ class Constant extends Result
   -- @treturn Constant
   @wrap: (val, name='(unknown)') ->
     typ = switch type val
-      when 'number' then Primitive.num
-      when 'string' then Primitive.str
+      when 'number' then T.num
+      when 'string' then T.str
       when 'table'
         if rawget val, '__base'
           -- a class
           switch ancestor val
-            when base.Op then Primitive.op
-            when base.Builtin then Primitive.builtin
+            when base.Op then T.opdef
+            when base.Builtin then T.builtin
             else
               error "#{name}: cannot wrap class '#{val.__name}'"
         elseif val.__class
           -- an instance
           switch ancestor val.__class
-            when scope.Scope then Primitive.scope
-            when base.FnDef then Primitive.fn
+            when scope.Scope then T.scope
+            when base.FnDef then T.fndef
             when Result then return val
             else
               error "#{name}: cannot wrap '#{val.__class.__name}' instance"
         else
           -- plain table
           val = scope.Scope.from_table val
-          Primitive.scope
+          T.scope
       else
         error "#{name}: cannot wrap Lua type '#{type val}'"
 
@@ -158,22 +155,22 @@ class Constant extends Result
   --- create a constant number.
   -- @tparam number num the number
   -- @treturn Constant
-  @num: (num) -> Constant Primitive.num, num, tostring num
+  @num: (num) -> Constant T.num, num, tostring num
 
   --- create a constant string.
   -- @tparam string str the string
   -- @treturn Constant
-  @str: (str) -> Constant Primitive.str, str, "'#{str}'"
+  @str: (str) -> Constant T.str, str, "'#{str}'"
 
   --- create a constant symbol.
   -- @tparam string sym the symbol
   -- @treturn Constant
-  @sym: (sym) -> Constant Primitive.sym, sym, sym
+  @sym: (sym) -> Constant T.sym, sym, sym
 
   --- create a constant boolean.
   -- @tparam boolean bool the boolean
   -- @treturn Constant
-  @bool: (bool) -> Constant Primitive.bool, bool, tostring bool
+  @bool: (bool) -> Constant T.bool, bool, tostring bool
 
   --- create a forced-literal Constant.
   --
diff --git a/alv/result/evt.moon b/alv/result/evt.moon
index bab502c..7e6a249 100644
--- a/alv/result/evt.moon
+++ b/alv/result/evt.moon
@@ -35,7 +35,10 @@ class EvtStream extends Result
 
   --- alias for `unwrap`.
   __call: (...) => @unwrap ...
-  __tostring: => "<#{@type}#{@metatype} #{@type\pp @value}>"
+
+  __tostring: =>
+    events = table.concat [@type\pp e for e in *@events], ' '
+    "<#{@type}#{@metatype} #{events}>"
 
   --- the type of this Result's value.
   -- @tfield type.Type type
@@ -79,7 +82,9 @@ class EvtStream extends Result
   --
   -- @classmethod
   -- @tparam type.Type type the type
-  new: (type) => super type
+  new: (type) =>
+    super type
+    @events = {}
 
 {
   :EvtStream
diff --git a/alv/result/sig.moon b/alv/result/sig.moon
index 73f06d1..b23afbe 100644
--- a/alv/result/sig.moon
+++ b/alv/result/sig.moon
@@ -3,7 +3,6 @@
 --
 -- @classmod SigStream
 import Result from require 'alv.result.base'
-import Primitive from require 'alv.type'
 
 class SigStream extends Result
 --- Result interface
@@ -79,33 +78,13 @@ class SigStream extends Result
 --- static functions
 -- @section static
 
-  --- construct a new SigStream.
+  --- construct a new Constant.
   --
   -- @classmethod
-  -- @tparam type.Type type the type
-  -- @tparam any value the Lua value to be accessed through `unwrap`
+  -- @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/rtnode.moon b/alv/rtnode.moon
index a8ebec3..61222ef 100644
--- a/alv/rtnode.moon
+++ b/alv/rtnode.moon
@@ -5,6 +5,9 @@
 -- between `Op`s.
 --
 -- @classmod RTNode
+
+import Error from require 'alv.error'
+
 class RTNode
 --- members
 -- @section members
@@ -41,15 +44,15 @@ class RTNode
   --- poll all IOStream instances that are effecting this (sub)tree.
   -- should be called once per frame on the root, right before tick.
   poll_io: =>
-    for stream, input in pairs @side_inputs
-      stream\poll! if input.io
+    for result, input in pairs @side_inputs
+      result\poll! if input.io
 
   --- in depth-first order, tick all Ops which have dirty Inputs.
   --
   -- short-circuits if there are no dirty Inputs in the entire subtree
   tick: =>
     any_dirty = false
-    for stream, input in pairs @side_inputs
+    for result, input in pairs @side_inputs
       if input\dirty!
         any_dirty = true
         break
@@ -70,7 +73,7 @@ class RTNode
 
       return unless self_dirty
 
-      @op\tick!
+      Error.wrap "ticking #{op}", @op\tick
 
   __tostring: =>
     buf = "<RT=#{@result}"
@@ -111,15 +114,15 @@ class RTNode
 
     @side_inputs, is_child = {}, {}
     for child in *@children
-      for stream, input in pairs child.side_inputs
-        @side_inputs[stream] = input
+      for result, input in pairs child.side_inputs
+        @side_inputs[result] = input
       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 input.io or not is_child[input.result]
+          @side_inputs[input.result] = input
 
     if @result and @result.metatype == '='
       assert not (next @side_inputs), "Const result has side_inputs"
diff --git a/alv/scope.moon b/alv/scope.moon
index b150280..4adf07d 100644
--- a/alv/scope.moon
+++ b/alv/scope.moon
@@ -5,7 +5,7 @@
 import Constant from require 'alv.result'
 import RTNode from require 'alv.rtnode'
 import Error from require 'alv.error'
-import Primitive from require 'alv.type'
+import T from require 'alv.type'
 
 class Scope
 --- members
@@ -57,7 +57,7 @@ class Scope
     child = @get start
     if not child
       error Error 'reference', "undefined symbol '#{start}'"
-    if child\type! != Primitive.scope
+    if child\type! != T.scope
       error Error 'reference', "'#{start}' is not a scope"
     child.result!\get rest, while_msg
 
diff --git a/alv/type.moon b/alv/type.moon
index 8a3708b..5c76b86 100644
--- a/alv/type.moon
+++ b/alv/type.moon
@@ -3,6 +3,7 @@
 --
 -- @module type
 import opairs from require 'alv.util'
+import result from require 'alv.cycle'
 
 shared_shape = (a, b) ->
   for key in pairs a
@@ -20,74 +21,54 @@ same = (a, b) ->
 
   true
 
---- Interface for types.
+--- Base class for types.
 -- @type Type
 class Type
-  new: =>
-
   --- pretty-print a value of this type.
   -- @function pp
   -- @tparam any value
   -- @treturn string
 
+  --- create a `SigStream` of this type.
+  -- @tparam ?any init initial value
+  -- @treturn SigStream
+  mk_sig: (init) =>
+    result.SigStream @, init
+
+  --- create a `EvtStream` of this type.
+  -- @treturn EvtStream
+  mk_evt: =>
+    result.EvtStream @
+
+  --- create a `Constant` of this type.
+  -- @tparam any val value
+  -- @treturn Constant
+  mk_const: (val) =>
+    result.Constant @, val
+
 --- Primitive type.
 --
--- Implements the `Type` interface.
+-- Extends `Type`.
 --
 -- @type Primitive
-class Primitive
+class Primitive extends Type
   pp: (value) => tostring value
 
-  __eq: (other) => @type == other.type
-  __tostring: => @type
-
-  --- shorthand for number type.
-  -- @tfield Primitive num
-  @num: @ 'num'
-
-  --- shorthand for string type.
-  -- @tfield Primitive str
-  @str: @ 'str'
-
-  --- shorthand for symbol type.
-  -- @tfield Primitive sym
-  @sym: @ 'sym'
-
-  --- shorthand for boolean type.
-  -- @tfield Primitive bool
-  @bool: @ 'bool'
-
-  --- shorthand for bang type.
-  -- @tfield Primitive bang
-  @bang: @ 'bang'
-
-  --- shorthand for `Scope` type.
-  -- @tfield Primitive scope
-  @scope: @ 'scope'
-
-  --- shorthand for `Op` type.
-  -- @tfield Primitive op
-  @op: @ 'opdef'
-
-  --- shorthand for `FnDef` type.
-  -- @tfield Primitive fn
-  @fn: @ 'fndef'
-
-  --- shorthand for `Builtin` type.
-  -- @tfield Primitive builtin
-  @builtin: @ 'builtin'
+  __eq: (other) => @name == other.name
+  __tostring: => @name
 
   --- instantiate a Primitive type.
   -- @classmethod
-  -- @tparam string type the typename
-  new: (@type) =>
+  -- @tparam string name the typename
+  new: (@name) =>
+    assert (type @name) == 'string', "Typename has to be a string: '#{@name}'"
 
 --- Struct/Hashmap type.
 --
--- Implements the `Type` interface.
+-- Extends `Type`.
 --
 -- @type Struct
-class Struct
+class Struct extends Type
   pp: (value) =>
     inner = table.concat ["#{k}: #{@types[k]\pp v}" for k, v in opairs value], ', '
     "{#{inner}}"
@@ -111,10 +92,10 @@ class Struct
 
 --- Array type.
 --
--- Implements the `Type` interface.
+-- Extends `Type`.
 --
 -- @type Array
-class Array
+class Array extends Type
   pp: (value) =>
     inner = table.concat [@type\pp v for v in *value], ' '
     "[#{inner}]"
@@ -128,7 +109,17 @@ class Array
   -- @tparam Type type
   new: (@size, @type) =>
 
+--- Magic table containing all `Primitive` types.
+--
+-- When indexed with a string returns a (cached) instance of that type.
+--
+-- @table T
+T = setmetatable {}, __index: (key) =>
+  with type = Primitive key
+    rawset @, key, type
+
 {
+  :T
   :Primitive
   :Array
   :Struct