Basic String escape

examples/demo.monkey

@@ -17,12 +17,12 @@ printBookName(book);
 
 let fibonacci = fn(x) {
   if (x == 0) {
-    0
+    return 0
   } else {
     if (x == 1) {
       return 1;
     } else {
-      fibonacci(x - 1) + fibonacci(x - 2);
+      return fibonacci(x - 1) + fibonacci(x - 2);
     }
   }
 };
@@ -30,13 +30,13 @@ let fibonacci = fn(x) {
 let map = fn(arr, f) {
   let iter = fn(arr, accumulated) {
     if (len(arr) == 0) {
-      accumulated
+      return accumulated
     } else {
-      iter(rest(arr), push(accumulated, f(first(arr))));
+      return iter(rest(arr), push(accumulated, f(first(arr))));
     }
   };
 
-  iter(arr, []);
+  return iter(arr, []);
 };
 
 let numbers = [1, 1 + 1, 4 - 1, 2 * 2, 2 + 3, 12 / 2];

lexer/lexer.go

@@ -1,6 +1,9 @@
 package lexer
 
-import "monkey/token"
+import (
+	"monkey/token"
+	"strings"
+)
 
 type Lexer struct {
 	input        string
@@ -179,14 +182,20 @@ func (l *Lexer) skipWhitespace() {
 }
 
 func (l *Lexer) readString() string {
-	position := l.position + 1
+	b := &strings.Builder{}
 	for {
 		l.readChar()
+		if l.ch == '\\' && l.peekChar() == '"' {
+			l.readChar()
+		} else {
 			if l.ch == '"' || l.ch == 0 {
 				break
 			}
 		}
-	return l.input[position:l.position]
+
+		b.WriteByte(l.ch)
+	}
+	return b.String()
 }
 
 func (l *Lexer) readLine() string {

lexer/lexer_test.go

@@ -32,6 +32,7 @@ func TestNextToken(t *testing.T) {
 				"foo bar"
 				[1, 2];
 				{"foo": "bar"}
+				"foo \"bar\""
 			`
 
 	tests := []struct {
@@ -137,7 +138,7 @@ func TestNextToken(t *testing.T) {
 		{token.COLON, ":"},
 		{token.STRING, "bar"},
 		{token.RBRACE, "}"},
-
+		{token.STRING, "foo \"bar\""},
 		{token.EOF, ""},
 	}