Crafting Interpreters - Part 18: Types of Values

This post is based on my notes from following the Crafting Interpreters book. The complete code and notes are available in this repository.

This part started fairly simple as Zig comes with tagged unions as a feature. Because of this I don't require some of the macros the book's code shows, such as AS_NUMBER or NUMBER_VAL. The biggest obstacle came from the runtimeError function, as Zig doesn't support variadic arguments, so I used anytype as the type of the second argument similar to how Zig does in their print functions. However, the obstacle didn't come from this but from a very mysterious compiler error, which I eventually figured out was because I needed to specify one of the arguments as comptime. Also, instead of the BINARY_OP macro I also had to write a function, made it take a comptime arg of a function that takes two f64 and returns a Value.

Challenges

1. Like we saw in a previous challenge, it's possible to replace subtraction with either (0 - value) or negating the operand before adding.

2. Some common instructions such as comparing with zero (less than 0, equal to 0, greater than 0) could be useful.