more builtins

builtins/chr.go

@@ -0,0 +1,19 @@
+package builtins
+
+import (
+	"fmt"
+	"monkey/object"
+)
+
+// Chr ...
+func Chr(args ...object.Object) object.Object {
+	if len(args) != 1 {
+		return newError("wrong number of arguments. got=%d, want=1",
+			len(args))
+	}
+
+	if i, ok := args[0].(*object.Integer); ok {
+		return &object.String{Value: fmt.Sprintf("%c", rune(i.Value))}
+	}
+	return newError("argument to `chr` not supported, got %s", args[0].Type())
+}