feat: add support for builtin delete (#127)

_test/delete0.go

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	a := map[string]int{"hello": 1, "world": 3}
+	delete(a, "hello")
+	fmt.Println(a)
+}
+
+// Output:
+// map[world:3]

interp/interp.go

@@ -155,6 +155,7 @@ func initUniverse() *Scope {
 		"cap":     &Symbol{kind: Bltn, builtin: _cap},
 		"close":   &Symbol{kind: Bltn, builtin: _close},
 		"copy":    &Symbol{kind: Bltn, builtin: _copy},
+		"delete":  &Symbol{kind: Bltn, builtin: _delete},
 		"len":     &Symbol{kind: Bltn, builtin: _len},
 		"make":    &Symbol{kind: Bltn, builtin: _make},
 		"new":     &Symbol{kind: Bltn, builtin: _new},

interp/interp_test.go

@@ -1899,6 +1899,29 @@ func main() {
 	// hello
 }
 
+func Example_delete0() {
+	src := `
+package main
+
+import "fmt"
+
+func main() {
+	a := map[string]int{"hello": 1, "world": 3}
+	delete(a, "hello")
+	fmt.Println(a)
+}
+`
+	i := interp.New(interp.Opt{Entry: "main"})
+	i.Use(stdlib.Value)
+	_, err := i.Eval(src)
+	if err != nil {
+		panic(err)
+	}
+
+	// Output:
+	// map[world:3]
+}
+
 func Example_export0() {
 	src := `
 package main

interp/run.go

@@ -1322,6 +1322,18 @@ func _close(n *Node) {
 	}
 }
 
+func _delete(n *Node) {
+	value0 := genValue(n.child[1]) // map
+	value1 := genValue(n.child[2]) // key
+	next := getExec(n.tnext)
+	var z reflect.Value
+
+	n.exec = func(f *Frame) Builtin {
+		value0(f).SetMapIndex(value1(f), z)
+		return next
+	}
+}
+
 func _len(n *Node) {
 	i := n.findex
 	value := genValue(n.child[1])