Comptime and Macros

Nitpick has two compile-time mechanisms:

	Macros	Comptime
Operates on	AST fragments	Values & types
Hygienic	Yes	N/A (no capture)
Type-checked?	After expansion	Yes, before evaluation
Pure?	Yes (rewriting)	Yes (no I/O)
Best for	Patterns, syntactic sugar	Math, reflection, tables

They cooperate: a macro can expand to a comptime(...) expression, and a comptime func: can call a macro-expanded helper.

Macro Expanding to Comptime

macro:square_const = (n) {
    comptime(n * n);
};

fixed int32:nine = square_const!(3);   // expands to comptime(3 * 3) = 9

This pattern gives you a name that looks like a function but always folds at the call site.

Comptime Calling Macros

A macro is expanded before the type checker runs, so by the time the const evaluator inspects a comptime func: body, all macro invocations inside it are already resolved.

macro:dbl = (x) { x + x; };

comptime func:quad = int32(int32:n) {
    pass dbl!(dbl!(n));
};

fixed int32:f = comptime(quad(3));   // 12

When to Choose Which

Choose macros when you need to manipulate code shape (statement generation, repeated patterns, conditional compilation cfg!).
Choose comptime when you need to compute values or inspect types.
Use both when you want a syntactic shorthand that resolves to a constant.

See guide/macros/README.md for the macro reference.