String literals and objects.

example/hello.wren

@@ -5,3 +5,4 @@ class Foo { // line comment
 }
 var a = Foo.new
 a.bar
+"a string"

src/compiler.c

@@ -105,6 +105,7 @@ static void expression(Compiler* compiler);
 static void call(Compiler* compiler);
 static void primary(Compiler* compiler);
 static void number(Compiler* compiler);
+static void string(Compiler* compiler);
 static TokenType peek(Compiler* compiler);
 static int match(Compiler* compiler, TokenType expected);
 static void consume(Compiler* compiler, TokenType expected);
@@ -339,6 +340,13 @@ void primary(Compiler* compiler)
     number(compiler);
     return;
   }
+
+  // String.
+  if (match(compiler, TOKEN_STRING))
+  {
+    string(compiler);
+    return;
+  }
 }
 
 void number(Compiler* compiler)
@@ -362,6 +370,27 @@ void number(Compiler* compiler)
   emit(compiler, constant);
 }
 
+void string(Compiler* compiler)
+{
+  Token* token = &compiler->parser->previous;
+
+  // TODO(bob): Handle escaping.
+
+  // Copy the string to the heap.
+  // Strip the surrounding "" off.
+  size_t length = token->end - token->start - 2;
+  char* text = malloc(length + 1);
+  strncpy(text, compiler->parser->source + token->start + 1, length);
+  text[length] = '\0';
+
+  // Define a constant for the literal.
+  int constant = addConstant(compiler, (Value)makeString(text));
+
+  // Compile the code to load the constant.
+  emit(compiler, CODE_CONSTANT);
+  emit(compiler, constant);
+}
+
 TokenType peek(Compiler* compiler)
 {
   return compiler->parser->current.type;

src/vm.c

@@ -113,6 +113,15 @@ ObjNum* makeNum(double number)
   return num;
 }
 
+ObjString* makeString(const char* text)
+{
+  ObjString* string = malloc(sizeof(ObjString));
+  string->obj.type = OBJ_STRING;
+  string->obj.flags = 0;
+  string->value = text;
+  return string;
+}
+
 ObjInstance* makeInstance(ObjClass* classObj)
 {
   ObjInstance* instance = malloc(sizeof(ObjInstance));
@@ -304,6 +313,10 @@ Value interpret(VM* vm, ObjBlock* block)
             classObj = vm->numClass;
             break;
 
+          case OBJ_STRING:
+            classObj = vm->stringClass;
+            break;
+
           case OBJ_INSTANCE:
             classObj = ((ObjInstance*)receiver)->classObj;
             break;
@@ -376,6 +389,10 @@ void printValue(Value value)
       printf("%f", ((ObjNum*)value)->value);
       break;
 
+    case OBJ_STRING:
+      printf("%s", ((ObjString*)value)->value);
+      break;
+
     case OBJ_BLOCK:
       printf("[block]");
       break;

src/vm.h

@@ -8,6 +8,7 @@
 
 typedef enum {
   OBJ_NUM,
+  OBJ_STRING,
   OBJ_BLOCK,
   OBJ_CLASS,
   OBJ_INSTANCE
@@ -33,6 +34,12 @@ typedef struct
   double value;
 } ObjNum;
 
+typedef struct
+{
+  Obj obj;
+  const char* value;
+} ObjString;
+
 typedef struct
 {
   Obj obj;
@@ -129,6 +136,7 @@ typedef struct
   ObjClass* blockClass;
   ObjClass* classClass;
   ObjClass* numClass;
+  ObjClass* stringClass;
 
   SymbolTable globalSymbols;
   // TODO(bob): Using a fixed array is gross here.
@@ -142,6 +150,9 @@ void freeVM(VM* vm);
 ObjClass* makeClass();
 ObjBlock* makeBlock();
 ObjNum* makeNum(double number);
+
+// Creates a new string object. Does not copy text.
+ObjString* makeString(const char* text);
 ObjInstance* makeInstance(ObjClass* classObj);
 
 // Initializes the symbol table.