[interpreter] (#18) Dynamically resolve types of Values.

Instead of having each `Value` type define `.type`, the type is now determined via a call to `__typeof` (and the scope via `__scopeof`). This allows the interpreter to be fully encapsulated, meaning that programs can freely modify the Kernel types (e.g., define new methods on `List`) without affecting other instances of the Interpreter.

spec/value_spec.cr → spec/interpreter/value_spec.cr

@@ -1,4 +1,4 @@
-require "./spec_helper.cr"
+require "../spec_helper.cr"
 
 describe "Values" do
   describe "::from_literal" do
@@ -40,10 +40,6 @@ describe "Values" do
 
 
   describe "TNil" do
-    it "has a type name of Nil" do
-      TNil.new.type.name.should eq("Nil")
-    end
-
     it "has a string representation of `nil`" do
       TNil.new.to_s.should eq("nil")
     end
@@ -66,10 +62,6 @@ describe "Values" do
   end
 
   describe "TBoolean" do
-    it "has a type name of Boolean" do
-      TBoolean.new(false).type.name.should eq("Boolean")
-    end
-
     it "always equates FALSE and FALSE" do
       TBoolean.new(false).should eq(TBoolean.new(false))
     end
@@ -108,10 +100,6 @@ describe "Values" do
   end
 
   describe "TInteger" do
-    it "has a type name of Integer" do
-      TInteger.new(1_i64).type.name.should eq("Integer")
-    end
-
     it "can contain any 64-bit integer value" do
       TInteger.new( 9_223_372_036_854_775_807)
       TInteger.new(-9_223_372_036_854_775_807)
@@ -146,10 +134,6 @@ describe "Values" do
   end
 
   describe "TFloat" do
-    it "has a type name of Float" do
-      TFloat.new(1.0).type.name.should eq("Float")
-    end
-
     it "can contain any 64-bit float value" do
       TFloat.new( 1.7976931348623157e+308)
       TFloat.new(-1.7976931348623157e+308)
@@ -184,10 +168,6 @@ describe "Values" do
   end
 
   describe "TString" do
-    it "has a type name of String" do
-      TString.new("").type.name.should eq("String")
-    end
-
     it "can contain strings of arbitrary length" do
       TString.new("hello"*1000)
     end
@@ -227,10 +207,6 @@ hi
   end
 
   describe "TSymbol" do
-    it "has a type name of Symbol" do
-      TSymbol.new("").type.name.should eq("Symbol")
-    end
-
     it "can be created from any string value" do
       TSymbol.new("hello"*1000)
       TSymbol.new("hello\n\t\0")
@@ -258,10 +234,6 @@ hi
 
 
   describe "TList" do
-    it "has a type name of List" do
-      TList.new.type.name.should eq("List")
-    end
-
     it "can be created with no elements" do
       TList.new
     end
@@ -296,10 +268,6 @@ hi
 
 
   describe "TMap" do
-    it "has a type name of Map" do
-      TMap.new.type.name.should eq("Map")
-    end
-
     it "can be created with no elements" do
       TMap.new
     end

src/myst/interpreter.cr

@@ -6,6 +6,7 @@ module Myst
   class Interpreter
     property stack : Array(Value)
     property self_stack : Array(Value)
+    property kernel = TModule.new("Kernel")
 
     property output : IO
     property errput : IO
@@ -14,32 +15,31 @@ module Myst
     def initialize(@output : IO = STDOUT, @errput : IO = STDERR)
       @stack = [] of Value
       @scope_stack = [] of Scope
-      @self_stack = [KERNEL] of Value
+      @self_stack = [@kernel] of Value
 
       init_kernel
     end
 
     private def init_kernel
-      KERNEL.scope.clear
-      KERNEL.scope["Nil"]         = NIL_TYPE
-      KERNEL.scope["Boolean"]     = BOOLEAN_TYPE
-      KERNEL.scope["Integer"]     = INTEGER_TYPE
-      KERNEL.scope["Float"]       = FLOAT_TYPE
-      KERNEL.scope["String"]      = STRING_TYPE
-      KERNEL.scope["Symbol"]      = SYMBOL_TYPE
-      KERNEL.scope["List"]        = LIST_TYPE
-      KERNEL.scope["Map"]         = MAP_TYPE
-      KERNEL.scope["Functor"]     = FUNCTOR_TYPE
-      KERNEL.scope["FunctorDef"]  = FUNCTOR_DEF_TYPE
-      KERNEL.scope["NativeDef"]   = NATIVE_DEF_TYPE
-      KERNEL.scope["Module"]      = MODULE_TYPE
-      KERNEL.scope["Type"]        = TYPE_TYPE
-      KERNEL.scope["IO"]          = IO_MODULE
+      init_nil
+      init_boolean
+      init_integer
+      init_float
+      init_string
+      init_symbol
+      init_list
+      init_map
+      init_io
+      # @kernel.scope["Functor"]     = FUNCTOR_TYPE
+      # @kernel.scope["FunctorDef"]  = FUNCTOR_DEF_TYPE
+      # @kernel.scope["NativeDef"]   = NATIVE_DEF_TYPE
+      # @kernel.scope["Module"]      = MODULE_TYPE
+      # @kernel.scope["Type"]        = TYPE_TYPE
     end
 
 
     def current_scope
-      scope_override || current_self.scope
+      scope_override || __scopeof(current_self)
     end
 
     def scope_override
@@ -74,7 +74,7 @@ module Myst
     end
 
     def put_error(error : RuntimeError)
-      value_to_s = error.value.scope["to_s"].as(TFunctor)
+      value_to_s = __scopeof(error.value)["to_s"].as(TFunctor)
       result = Invocation.new(self, value_to_s, error.value, [] of Value, nil).invoke
       @errput.puts(result.as(TString).value)
     end

src/myst/interpreter/native_lib.cr

@@ -13,7 +13,7 @@ module Myst
     # Same as `call_func`, but the function to call is given as a name to
     # look up on the given receiver.
     def call_func_by_name(itr, receiver : Value, name : String, args : Array(Value))
-      func = receiver.scope[name].as(TFunctor)
+      func = itr.__scopeof(receiver)[name].as(TFunctor)
       Invocation.new(itr, func, receiver, args, nil).invoke
     end
   end

src/myst/interpreter/native_lib/boolean.cr

@@ -1,31 +1,38 @@
 module Myst
-  BOOLEAN_TYPE.instance_scope["to_s"] = TFunctor.new([
-    TNativeDef.new(0) do |this, _args, _block, _itr|
-      TString.new(this.as(TBoolean).value ? "true" : "false")
-    end
-  ] of Callable)
+  class Interpreter
+    def init_boolean
+      bool_type = TType.new("Boolean")
+      bool_type.instance_scope["to_s"] = TFunctor.new([
+        TNativeDef.new(0) do |this, _args, _block, _itr|
+          TString.new(this.as(TBoolean).value ? "true" : "false")
+        end
+      ] of Callable)
 
-  BOOLEAN_TYPE.instance_scope["=="] = TFunctor.new([
-    TNativeDef.new(1) do |this, (arg), _block, _itr|
-      this = this.as(TBoolean)
-      case arg
-      when TBoolean
-        TBoolean.new(this.value == arg.value)
-      else
-        TBoolean.new(false)
-      end
-    end
-  ] of Callable)
+      bool_type.instance_scope["=="] = TFunctor.new([
+        TNativeDef.new(1) do |this, (arg), _block, _itr|
+          this = this.as(TBoolean)
+          case arg
+          when TBoolean
+            TBoolean.new(this.value == arg.value)
+          else
+            TBoolean.new(false)
+          end
+        end
+      ] of Callable)
+
+      bool_type.instance_scope["!="] = TFunctor.new([
+        TNativeDef.new(1) do |this, (arg), _block, _itr|
+          this = this.as(TBoolean)
+          case arg
+          when TBoolean
+            TBoolean.new(this.value != arg.value)
+          else
+            TBoolean.new(true)
+          end
+        end
+      ] of Callable)
 
-  BOOLEAN_TYPE.instance_scope["!="] = TFunctor.new([
-    TNativeDef.new(1) do |this, (arg), _block, _itr|
-      this = this.as(TBoolean)
-      case arg
-      when TBoolean
-        TBoolean.new(this.value != arg.value)
-      else
-        TBoolean.new(true)
-      end
+      @kernel.scope["Boolean"] = bool_type
     end
-  ] of Callable)
+  end
 end