constant dissasemble

src/chunk.zig

@@ -5,6 +5,7 @@ const ValueArray = value.ValueArray;
 
 pub const OpCode = enum(u8) {
     OP_RETURN,
+    OP_CONSTANT,
 };
 
 pub const Chunk = struct {
@@ -62,6 +63,7 @@ pub const Chunk = struct {
         const instruction = self.code[offset];
         switch (instruction) {
             @intFromEnum(OpCode.OP_RETURN) => return simple_instruction("OP_RETURN", offset),
+            @intFromEnum(OpCode.OP_CONSTANT) => return self.constant_instruction("OP_CONSTANT", offset),
             else => {
                 print("unknown opcode {d}\n", .{instruction});
                 return offset + 1;
@@ -78,6 +80,15 @@ pub const Chunk = struct {
         self.allocator.free(self.code);
         self.constants.deinit();
     }
+    fn constant_instruction(self: *Chunk, comptime name: []const u8, offset: usize) usize {
+        const constant_addr = self.code[offset + 1];
+        const constant_value = self.constants.values[constant_addr];
+
+        print("{s} ", .{name});
+        print_value(constant_value);
+        print("\n", .{});
+        return offset + 2;
+    }
 };
 
 fn simple_instruction(comptime name: []const u8, offset: usize) usize {
@@ -85,6 +96,10 @@ fn simple_instruction(comptime name: []const u8, offset: usize) usize {
     return offset + 1;
 }
 
+fn print_value(v: value.Value) void {
+    print("{d}", .{v});
+}
+
 inline fn grow_capacity(old: usize) usize {
     return if (old < 8) 8 else old * 2;
 }

src/main.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const chunk = @import("./chunk.zig");
+const OpCode = chunk.OpCode;
 
 pub fn main() !void {
     // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
@@ -11,10 +12,12 @@ pub fn main() !void {
     var c = try chunk.Chunk.init(alloc);
     defer c.deinit();
 
-    try c.write(@intFromEnum(chunk.OpCode.OP_RETURN));
     try c.write(@intFromEnum(chunk.OpCode.OP_RETURN));
 
-    _ = try c.add_constant(0.0);
+    const constant_idx = try c.add_constant(1.2);
+    try c.write(@intFromEnum(OpCode.OP_CONSTANT));
+    try c.write(@truncate(constant_idx));
+
     c.dissasemble_chunk("test chunk");
 }