add SetGlobal/SetGlobalLong opcodes

- main: split compile/runtime error messages

src/chunk.zig

@@ -33,6 +33,8 @@ const AllOpcodes = struct {
     pub DefineGlobalLong: u8 = 18,
     pub GetGlobal: u8 = 19,
     pub GetGlobalLong: u8 = 20,
+    pub SetGlobal: u8 = 21,
+    pub SetGlobalLong: u8 = 22,
 };
 
 pub const OpCode = AllOpcodes{};
@@ -245,6 +247,10 @@ pub const Chunk = struct {
             return try constantInstruction(stdout, "OP_GETGLOBAL", self, index);
         } else if (instruction == OpCode.GetGlobalLong) {
             return try constantLongInstruction(stdout, "OP_GETGLOBAL_LONG", self, index);
+        } else if (instruction == OpCode.SetGlobal) {
+            return try constantInstruction(stdout, "OP_SETGLOBAL", self, index);
+        } else if (instruction == OpCode.SetGlobalLong) {
+            return try constantLongInstruction(stdout, "OP_SETGLOBAL_LONG", self, index);
         } else {
             try stdout.print("Unknown opcode: {}\n", instruction);
             return index + 1;

src/compiler.zig

@@ -39,7 +39,7 @@ const Precedence = enum(u5) {
     Primary,
 };
 
-const ParseFn = fn (*Compiler) anyerror!void;
+const ParseFn = fn (*Compiler, bool) anyerror!void;
 
 const ParseRule = struct {
     prefix: ?ParseFn = null,
@@ -229,13 +229,13 @@ pub const Compiler = struct {
         }
     }
 
-    fn grouping(self: *Compiler) !void {
+    fn grouping(self: *Compiler, canAssign: bool) !void {
         try self.expression();
         try self.consume(.RIGHT_PAREN, "Expect ')' after expression.");
     }
 
     /// Emits bytecode for a number being loaded into the code.
-    fn number(self: *Compiler) !void {
+    fn number(self: *Compiler, canAssign: bool) !void {
         var value: f64 = try std.fmt.parseFloat(
             f64,
             self.parser.previous.lexeme,
@@ -243,7 +243,7 @@ pub const Compiler = struct {
         try self.emitConstant(values.NumberVal(value));
     }
 
-    fn string(self: *Compiler) !void {
+    fn string(self: *Compiler, canAssign: bool) !void {
         const lexeme_len = self.parser.previous.lexeme.len;
 
         try self.emitConstant(values.ObjVal(try objects.copyString(
@@ -252,7 +252,7 @@ pub const Compiler = struct {
         )));
     }
 
-    fn namedVariable(self: *Compiler, tok: *Token) !void {
+    fn namedVariable(self: *Compiler, tok: *Token, canAssign: bool) !void {
         // writeConstant always writes OP_CODE which may be not
         // what we want, so.
         var idx = try self.currentChunk().writeConstantRaw(values.ObjVal(try objects.copyString(
@@ -260,19 +260,28 @@ pub const Compiler = struct {
             tok.lexeme,
         )), tok.line);
 
-        try self.emitConstWithIndex(
-            chunks.OpCode.GetGlobal,
-            chunks.OpCode.GetGlobalLong,
-            idx,
-        );
+        if (canAssign and try self.match(.EQUAL)) {
+            try self.expression();
+            try self.emitConstWithIndex(
+                chunks.OpCode.SetGlobal,
+                chunks.OpCode.SetGlobalLong,
+                idx,
+            );
+        } else {
+            try self.emitConstWithIndex(
+                chunks.OpCode.GetGlobal,
+                chunks.OpCode.GetGlobalLong,
+                idx,
+            );
+        }
     }
 
-    fn variable(self: *Compiler) !void {
-        try self.namedVariable(&self.parser.previous);
+    fn variable(self: *Compiler, canAssign: bool) !void {
+        try self.namedVariable(&self.parser.previous, canAssign);
     }
 
     /// Emits bytecode for a given unary.
-    fn unary(self: *Compiler) !void {
+    fn unary(self: *Compiler, canAssign: bool) !void {
         var ttype = self.parser.previous.ttype;
         try self.parsePrecedence(.Unary);
 
@@ -283,7 +292,7 @@ pub const Compiler = struct {
         }
     }
 
-    fn binary(self: *Compiler) !void {
+    fn binary(self: *Compiler, canAssign: bool) !void {
         var op_type = self.parser.previous.ttype;
         var rule: *ParseRule = self.getRule(op_type);
         try self.parsePrecedence(@intToEnum(Precedence, @enumToInt(rule.precedence) + 1));
@@ -306,7 +315,7 @@ pub const Compiler = struct {
         }
     }
 
-    fn literal(self: *Compiler) !void {
+    fn literal(self: *Compiler, canAssign: bool) !void {
         switch (self.parser.previous.ttype) {
             .FALSE => try self.emitByte(OpCode.False),
             .NIL => try self.emitByte(OpCode.Nil),
@@ -315,21 +324,27 @@ pub const Compiler = struct {
         }
     }
 
-    fn parsePrecedence(self: *Compiler, precedence: Precedence) !void {
+    fn parsePrecedence(self: *Compiler, precedence: Precedence) anyerror!void {
         try self.advance();
         var as_int = @enumToInt(precedence);
         var prefix_rule_opt = self.getRule(self.parser.previous.ttype).prefix;
 
         if (prefix_rule_opt) |prefix_rule| {
-            try prefix_rule(self);
+            var canAssign: bool = as_int <= @enumToInt(Precedence.Assignment);
+            try prefix_rule(self, canAssign);
 
             while (as_int <= @enumToInt(self.getRule(self.parser.current.ttype).precedence)) {
                 try self.advance();
                 var infix_rule_opt = self.getRule(self.parser.previous.ttype).infix;
                 if (infix_rule_opt) |infix_rule| {
-                    try infix_rule(self);
+                    try infix_rule(self, canAssign);
                 }
             }
+
+            if (canAssign and try self.match(.EQUAL)) {
+                self.errorPrevious("Invalid assignment target.");
+                try self.expression();
+            }
         } else {
             self.errorPrevious("Expect expression.");
             return;
@@ -340,7 +355,7 @@ pub const Compiler = struct {
         return &rules[@enumToInt(ttype)];
     }
 
-    fn expression(self: *Compiler) !void {
+    fn expression(self: *Compiler) anyerror!void {
         try self.parsePrecedence(.Assignment);
     }
 
@@ -376,7 +391,7 @@ pub const Compiler = struct {
         self: *Compiler,
         token: *Token,
     ) !chunks.ConstantIndex {
-        return try self.currentChunk().writeConstant(values.ObjVal(try objects.copyString(
+        return try self.currentChunk().writeConstantRaw(values.ObjVal(try objects.copyString(
             self.vmach,
             token.lexeme,
         )), token.line);

src/main.zig

@@ -79,8 +79,11 @@ fn runPrompt(allocator: *Allocator) !void {
         runWithVM(&vmach, line) catch |err| {
             switch (err) {
                 InterpretResult.Ok => {},
-                InterpretResult.CompileError, InterpretResult.RuntimeError => blk: {
-                    try stdout.print("compile/runtime error.\n");
+                InterpretResult.CompileError => blk: {
+                    try stdout.print("compile error.\n");
+                },
+                InterpretResult.RuntimeError => blk: {
+                    try stdout.print("runtime error.\n");
                 },
                 else => return err,
             }

src/vm.zig

@@ -245,6 +245,17 @@ pub const VM = struct {
         }
     }
 
+    fn doSetGlobal(self: *VM, name: []u8) !void {
+        var res = try self.globals.getOrPut(name);
+
+        if (res.found_existing) {
+            res.kv.value = self.peek(0);
+        } else {
+            self.runtimeError("Undefined variable '{}'.", name);
+            return InterpretResult.RuntimeError;
+        }
+    }
+
     fn run(self: *VM) !void {
         while (true) {
             if (self.debug_flag) {
@@ -295,6 +306,15 @@ pub const VM = struct {
                     break :blk;
                 },
 
+                chunk.OpCode.SetGlobal => blk: {
+                    try self.doSetGlobal(self.readString());
+                    break :blk;
+                },
+                chunk.OpCode.SetGlobalLong => blk: {
+                    try self.doSetGlobal(self.readStringLong());
+                    break :blk;
+                },
+
                 // extracting the name is different depending of the
                 // op code since one just uses a single byte, the other
                 // uses three bytes since its a u24.