feat: interpret callable values

glox/ast/ast.go

@@ -263,7 +263,7 @@ func parenthesize(name ExpType, value string) string {
 
  out.WriteString("(" + string(name) + " ")
  out.WriteString(value)
- out.WriteString(" )")
+ out.WriteString(")")
 
  return out.String()
 }

glox/interpreter/interpreter.go

@@ -5,6 +5,7 @@ import (
  "glox/ast"
  "glox/env"
  "glox/exception"
+ "glox/object"
  "glox/token"
  "io"
  "math"
@@ -319,6 +320,41 @@ func (i *Interpreter) VisitWhile(exp *ast.WhileStmt) any {
  return nil
 }
 
+func (i *Interpreter) VisitCall(expr *ast.Call) any {
+ calle := i.evaluate(expr.Callee)
+ err, isErr := calle.(error)
+ if !isErr {
+ args := []any{}
+ for _, arg := range expr.Args {
+ val := i.evaluate(arg)
+ if err, isErr = val.(error); isErr {
+ break
+ }
+ args = append(args, val)
+ }
+ if err != nil {
+ return err
+ }
+ function, isOk := calle.(object.Callable[*Interpreter])
+ if !isOk {
+ return exception.Runtime(expr.Paren, fmt.Sprintf("'%v' cannot be called.", expr.Callee.String()))
+ } else if function.Arity() != len(args) {
+ want, got := function.Arity(), len(args)
+ var msg string
+ if got > want {
+ msg = fmt.Sprintf("too many arguments passed. expected %d but got %d.", want, got)
+ } else {
+ msg = fmt.Sprintf("not enough arguments passed. expected %d but got %d.", want, got)
+ }
+ return exception.Runtime(expr.Paren, msg)
+ }
+ return function.Call(i, args)
+ }
+
+ return err
+
+}
+
 func (i *Interpreter) execLoop(loop *ast.WhileStmt) (res any, err error) {
  //FIXME: The `continue` statement doesn't seem to work as expected.
  defer func() {

glox/object/object.go

@@ -0,0 +1,6 @@
+package object
+
+type Callable[T any] interface {
+ Call(i T, arguments []any) any
+ Arity() int
+}