Extra Features

object/builtins.go

@@ -1,6 +1,12 @@
 package object
 
-import "fmt"
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"unicode/utf8"
+)
 
 var Builtins = []struct {
 	Name    string
@@ -18,7 +24,7 @@ var Builtins = []struct {
 			case *Array:
 				return &Integer{Value: int64(len(arg.Elements))}
 			case *String:
-				return &Integer{Value: int64(len(arg.Value))}
+				return &Integer{Value: int64(utf8.RuneCountInString(arg.Value))}
 			default:
 				return newError("argument to `len` not supported, got %s",
 					args[0].Type())
@@ -27,7 +33,30 @@ var Builtins = []struct {
 		},
 	},
 	{
-		"puts",
+		"input",
+		&Builtin{Fn: func(args ...Object) Object {
+			if len(args) > 0 {
+				obj, ok := args[0].(*String)
+				if !ok {
+					return newError(
+						"argument to `input` not supported, got %s",
+						args[0].Type(),
+					)
+				}
+				fmt.Fprintf(os.Stdout, obj.Value)
+			}
+
+			buffer := bufio.NewReader(os.Stdin)
+
+			line, _, err := buffer.ReadLine()
+			if err != nil && err != io.EOF {
+				return newError(fmt.Sprintf("error reading input from stdin: %s", err))
+			}
+			return &String{Value: string(line)}
+		}},
+	},
+	{
+		"print",
 		&Builtin{Fn: func(args ...Object) Object {
 			for _, arg := range args {
 				fmt.Println(arg.Inspect())
@@ -123,6 +152,48 @@ var Builtins = []struct {
 		},
 		},
 	},
+	{
+		"pop",
+		&Builtin{Fn: func(args ...Object) Object {
+			if len(args) != 1 {
+				return newError("wrong number of arguments. got=%d, want=1",
+					len(args))
+			}
+			if args[0].Type() != ARRAY_OBJ {
+				return newError("argument to `pop` must be ARRAY, got %s",
+					args[0].Type())
+			}
+
+			arr := args[0].(*Array)
+			length := len(arr.Elements)
+
+			if length == 0 {
+				return newError("cannot pop from an empty array")
+			}
+
+			element := arr.Elements[length-1]
+			arr.Elements = arr.Elements[:length-1]
+
+			return element
+		},
+		},
+	},
+	{
+		"exit",
+		&Builtin{Fn: func(args ...Object) Object {
+			if len(args) == 1 {
+				if args[0].Type() != INTEGER_OBJ {
+					return newError("argument to `exit` must be INTEGER, got %s",
+						args[0].Type())
+				}
+				os.Exit(int(args[0].(*Integer).Value))
+			} else {
+				os.Exit(0)
+			}
+			return nil
+		},
+		},
+	},
 }
 
 func newError(format string, a ...interface{}) *Error {