rearrange builtins

builtins/find.go

@@ -0,0 +1,36 @@
+package builtins
+
+import "monkey/object"
+
+import (
+	"strings"
+)
+
+// Find ...
+func Find(args ...object.Object) object.Object {
+	if len(args) != 2 {
+		return newError("wrong number of arguments. got=%d, want=2",
+			len(args))
+	}
+
+	if haystack, ok := args[0].(*object.String); ok {
+		if needle, ok := args[1].(*object.String); ok {
+			index := strings.Index(haystack.Value, needle.Value)
+			return &object.Integer{Value: int64(index)}
+		} else {
+			return newError("expected arg #2 to be `str` got got=%T", args[1])
+		}
+	} else if haystack, ok := args[0].(*object.Array); ok {
+		needle := args[1]
+		index := -1
+		for i, el := range haystack.Elements {
+			if cmp, ok := el.(object.Comparable); ok && cmp.Equal(needle) {
+				index = i
+				break
+			}
+		}
+		return &object.Integer{Value: int64(index)}
+	} else {
+		return newError("expected arg #1 to be `str` or `array` got got=%T", args[0])
+	}
+}