1 files changed, 106 insertions, 0 deletions
diff --git a/core/const.moon b/core/const.moon
new file mode 100644
index 0000000..564ab53
--- /dev/null
+++ b/core/const.moon
@@ -0,0 +1,106 @@
+import Op, Action from require 'core.base'
+
+local Scope
+load_ = ->
+  import Scope from require 'core.scope'
+
+ancestor = (klass) ->
+  assert klass, "cant find the ancestor of nil"
+  while klass.__parent
+    klass = klass.__parent
+  klass
+
+class Const
+  types = {
+    sym: true
+    str: true
+    num: true
+    scope: true
+    op: true
+    opdef: true
+    fndef: true
+    builtin: true
+  }
+
+  new: (@type, @value, @raw) =>
+    assert types[@type], "invalid Const type: #{@type}"
+
+-- Value interface
+  get: (type) =>
+    assert not type or type == @type, "#{@} is not a #{type}"
+    @value
+
+  getc: (type) =>
+    assert not type or type == @type, "#{@} is not a #{type}"
+    @value
+
+  update: (dt) =>
+    switch @type
+      when 'op'
+        @value\update dt
+
+-- AST interface
+  eval: (scope) =>
+    switch @type
+      when 'num', 'str'
+        @
+      when 'sym'
+        assert (scope\get @value), "undefined reference to symbol '#{@value}'"
+      else
+        error "cannot evaluate #{@}"
+
+  quote: => @
+
+  stringify: => @raw
+
+-- static
+  __tostring: =>
+    value = if @type == 'opdef' or @type == 'builtin' then @value.__name else @value
+    "<#{@type}: #{value}>"
+
+  __eq: (other) =>
+    other.type == @type and other.value == @value
+
+  unescape = (str) -> str\gsub '\\([\'"\\])', '%1'
+
+  @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
+
+  @num: (num) -> Const 'num', num, tostring num
+  @str: (str) -> Const 'str', str, "'#{str}'"
+  @sym: (sym) -> Const 'sym', sym, sym
+  @empty: -> Const 'str', '', "''"
+
+  @wrap: (val, name='(unknown)') ->
+    typ = switch type val
+      when 'number' then 'num'
+      when 'string' then 'str'
+      when 'table'
+        if base = rawget val, '__base'
+          -- a class
+          switch ancestor val
+            when Op then 'opdef'
+            when Action then 'builtin'
+            else
+              error "#{name}: cannot wrap class '#{val.__name}'"
+        elseif val.__class
+          -- an instance
+          switch ancestor val.__class
+            when Op then 'op'
+            when Scope then 'scope'
+            when Const
+              return val
+            else
+              error "#{name}: cannot wrap '#{val.__class.__name}' instance"
+        else
+          -- plain table
+          return Const 'scope', Scope.from_table val
+      else
+        error "#{name}: cannot wrap Lua type '#{type val}'"
+
+    Const typ, val
+
+:Const, :load_