eval: add len

README.md

@@ -9,9 +9,8 @@
 - Destructuring assignment
 - `maptable`
 - `coerce`
-- `len`
 - `mac`
-- `\``
+- `````
 - `w/link`
 - `aform`
 - ...

ast/ast.go

@@ -94,14 +94,14 @@ func (ast *AST) Pretty() string {
 			rest = " . " + *val.Rest
 		}
 		// TODO: opt
-    opt := ""
+		opt := ""
 		iter := val.Opt.IterFunc()
 		for kv, ok := iter(); ok; kv, ok = iter() {
-      opt += "(o " + kv.Key.(string) + " " + kv.Value.(*AST).Pretty() + ")"
-    }
-    if val.HasOpt() && (val.HasRest() || len(agg) != 0) {
-      opt = " " + opt
-    }
+			opt += "(o " + kv.Key.(string) + " " + kv.Value.(*AST).Pretty() + ")"
+		}
+		if val.HasOpt() && (val.HasRest() || len(agg) != 0) {
+			opt = " " + opt
+		}
 		body := val.Body.Pretty()
 		return "(fn (" + strings.Join(agg, " ") + rest + opt + ") " + body + ")"
 	} else if ast.Tag == Char {
@@ -167,5 +167,5 @@ func (f *Func) HasRest() bool {
 }
 
 func (f *Func) HasOpt() bool {
-  return f.Opt.Len() != 0
+	return f.Opt.Len() != 0
 }

eval/eval.go

@@ -26,6 +26,7 @@ func RootEnv() ast.Env {
 		"pr":    evalPr,
 		"table": evalTable,
 		"type":  evalType,
+		"len":   evalLen,
 	}
 
 	for k, v := range prims {
@@ -302,7 +303,7 @@ func evalFn(input []*ast.AST, e ast.Env) (*ast.AST, error) {
 
 	body := input[1]
 
-  fe := ast.NewEnv(&e)
+	fe := ast.NewEnv(&e)
 
 	res := ast.AST{ast.Fn, ast.Func{argsStr, rest, opt, body, fe}}
 	return &res, nil
@@ -453,6 +454,33 @@ func evalType(l []*ast.AST) (*ast.AST, error) {
 	return l[0].Type(), nil
 }
 
+func evalLen(l []*ast.AST) (*ast.AST, error) {
+	err := checkArity(l, 1, "len")
+
+	if err != nil {
+		return nil, err
+	}
+
+	cnt := 0
+	elem := l[0]
+
+	switch elem.Tag {
+	case ast.Quoted:
+		// TODO: error handling
+		cnt = len(elem.Val.(*ast.AST).Val.([]*ast.AST))
+	case ast.String:
+		cnt = len(elem.Val.(string))
+	case ast.Table:
+		cnt = len(elem.Val.(map[*ast.AST]*ast.AST))
+	default:
+		return nil, fmt.Errorf("Cannot get length of %s", elem.Pretty())
+	}
+
+	res := ast.AST{ast.Num, float64(cnt)}
+
+	return &res, nil
+}
+
 func evalSymbolList(l []*ast.AST, e ast.Env) (*ast.AST, error) {
 	sym := l[0].Val.(string)