type checking and error handling for builtins improved.

object/closure.go

@@ -11,12 +11,18 @@ type CompiledFunction struct {
 	NumParameters int
 }
 
+func (cf *CompiledFunction) Bool() bool {
+	return true
+}
+
 func (cf *CompiledFunction) Type() ObjectType {
 	return COMPILED_FUNCTION_OBJ
 }
+
 func (cf *CompiledFunction) Inspect() string {
 	return fmt.Sprintf("CompiledFunction[%p]", cf)
 }
+
 func (cf *CompiledFunction) String() string {
 	return cf.Inspect()
 }
@@ -26,12 +32,18 @@ type Closure struct {
 	Free []Object
 }
 
+func (c *Closure) Bool() bool {
+	return true
+}
+
 func (c *Closure) Type() ObjectType {
 	return CLOSURE_OBJ
 }
+
 func (c *Closure) Inspect() string {
 	return fmt.Sprintf("Closure[%p]", c)
 }
+
 func (c *Closure) String() string {
 	return c.Inspect()
 }