evaluator: Add move and line to builtins

Add `move` and `line` to builtins. Add `\n` to print function.
Restructure Builtins such that we can extract parser builtins as map
[string]*parser.FuncDecl, this is necessary for custom builtins to flow
through from evaluator to parser. Builtin definition should happen in
one place only.

pkg/evaluator/builtin.go

@@ -3,30 +3,63 @@ package evaluator
 import (
 	"strconv"
 	"strings"
+
+	"foxygo.at/evy/pkg/parser"
 )
 
-type Builtin func(args []Value) Value
+type Builtin struct {
+	Func BuiltinFunc
+	Decl *parser.FuncDecl
+}
+
+type Builtins map[string]Builtin
+
+func (b Builtins) Decls() map[string]*parser.FuncDecl {
+	decls := make(map[string]*parser.FuncDecl, len(b))
+	for name, builtin := range b {
+		decls[name] = builtin.Decl
+	}
+	return decls
+}
+
+type BuiltinFunc func(args []Value) Value
 
-func (b Builtin) Type() ValueType { return BUILTIN }
-func (b Builtin) String() string  { return "builtin function" }
+func (b BuiltinFunc) Type() ValueType { return BUILTIN }
+func (b BuiltinFunc) String() string  { return "builtin function" }
 
-func newBuiltins(e *Evaluator) map[string]Builtin {
-	return map[string]Builtin{
-		"print": Builtin(e.Print),
-		"len":   Builtin(Len),
+func DefaultBuiltins(print func(string)) Builtins {
+	return Builtins{
+		"print": {Func: printFunc(print), Decl: printDecl},
+		"len":   {Func: BuiltinFunc(lenFunc), Decl: lenDecl},
+		"move":  {Func: moveFunc(print), Decl: moveDecl},
+		"line":  {Func: lineFunc(print), Decl: lineDecl},
 	}
 }
 
-func (e *Evaluator) Print(args []Value) Value {
-	argList := make([]string, len(args))
-	for i, arg := range args {
-		argList[i] = arg.String()
+var printDecl = &parser.FuncDecl{
+	Name:          "print",
+	VariadicParam: &parser.Var{Name: "a", T: parser.ANY_TYPE},
+	ReturnType:    parser.NONE_TYPE,
+}
+
+func printFunc(printFn func(string)) BuiltinFunc {
+	return func(args []Value) Value {
+		argList := make([]string, len(args))
+		for i, arg := range args {
+			argList[i] = arg.String()
+		}
+		printFn(strings.Join(argList, " ") + "\n")
+		return nil
 	}
-	e.print(strings.Join(argList, " "))
-	return nil
 }
 
-func Len(args []Value) Value {
+var lenDecl = &parser.FuncDecl{
+	Name:       "len",
+	Params:     []*parser.Var{{Name: "a", T: parser.ANY_TYPE}},
+	ReturnType: parser.NUM_TYPE,
+}
+
+func lenFunc(args []Value) Value {
 	if len(args) != 1 {
 		return newError("'len' takes 1 argument not " + strconv.Itoa(len(args)))
 	}
@@ -37,8 +70,38 @@ func Len(args []Value) Value {
 		return &Num{Val: float64(len(arg.Elements))}
 	case *String:
 		return &Num{Val: float64(len(arg.Val))}
-	default:
-		return newError("'len' takes 1 argument of type 'string', array '[]' or map '{}' not " + args[0].Type().String())
 	}
+	return newError("'len' takes 1 argument of type 'string', array '[]' or map '{}' not " + args[0].Type().String())
+}
+
+var moveDecl = &parser.FuncDecl{
+	Name: "move",
+	Params: []*parser.Var{
+		&parser.Var{Name: "x", T: parser.NUM_TYPE},
+		&parser.Var{Name: "y", T: parser.NUM_TYPE},
+	},
+	ReturnType: parser.NUM_TYPE,
+}
+
+func moveFunc(printFn func(string)) BuiltinFunc {
+	return func(args []Value) Value {
+		printFn("'move' not yet implemented\n")
+		return nil
+	}
+}
 
+var lineDecl = &parser.FuncDecl{
+	Name: "line",
+	Params: []*parser.Var{
+		&parser.Var{Name: "x", T: parser.NUM_TYPE},
+		&parser.Var{Name: "y", T: parser.NUM_TYPE},
+	},
+	ReturnType: parser.NUM_TYPE,
+}
+
+func lineFunc(printFn func(string)) BuiltinFunc {
+	return func(args []Value) Value {
+		printFn("'line' not yet implemented\n")
+		return nil
+	}
 }

pkg/evaluator/evaluator.go

@@ -5,10 +5,11 @@ import (
 )
 
 func Run(input string, print func(string)) {
-	p := parser.New(input)
+	builtins := DefaultBuiltins(print)
+	p := parser.NewWithBuiltins(input, builtins.Decls())
 	prog := p.Parse()
 	e := &Evaluator{print: print}
-	e.builtins = newBuiltins(e)
+	e.builtins = builtins
 	val := e.Eval(prog, newScope())
 	if isError(val) {
 		print(val.String())
@@ -72,7 +73,7 @@ func (e *Evaluator) evalFunctionCall(funcCall *parser.FunctionCall, scope *scope
 	if !ok {
 		return newError("cannot find builtin function " + funcCall.Name)
 	}
-	return builtin(args)
+	return builtin.Func(args)
 }
 
 func (e *Evaluator) evalVar(v *parser.Var, scope *scope) Value {

pkg/evaluator/evaluator_test.go

@@ -9,7 +9,7 @@ import (
 
 func TestBasicEval(t *testing.T) {
 	in := "a:=1\n print a 2"
-	want := "1 2"
+	want := "1 2\n"
 	b := bytes.Buffer{}
 	fn := func(s string) { b.WriteString(s) }
 	Run(in, fn)
@@ -30,7 +30,7 @@ func TestParseDeclaration(t *testing.T) {
 			b := bytes.Buffer{}
 			fn := func(s string) { b.WriteString(s) }
 			Run(in, fn)
-			assert.Equal(t, want, b.String())
+			assert.Equal(t, want+"\n", b.String())
 		})
 	}
 }
@@ -48,6 +48,10 @@ end`
 	b := bytes.Buffer{}
 	fn := func(s string) { b.WriteString(s) }
 	Run(prog, fn)
-	want := "x: 12"
+	want := `
+'move' not yet implemented
+'line' not yet implemented
+x: 12
+`[1:]
 	assert.Equal(t, want, b.String())
 }