Comptime

Nitpick comptime is the compile-time function evaluation (CTFE) layer. Code marked comptime is reduced to a constant value during compilation, so the resulting binary contains only the answer — never the computation.

Contents

• basic.md — comptime(expr), comptime { ... }, comptime func:
• ctfe.md — How CTFE works: const folding, recursion, memoization
• intrinsics.md — @typeInfo, @sizeof, @alignof, @len, @fieldType, @offsetof
• generics.md — T: type parameters and type-level dispatch
• macros.md — Comptime vs. macros (and how they cooperate)
• limits.md — limit<Rules> short-circuit and assert_static
• limitations.md — What is not allowed at comptime
• debug.md — Reading comptime diagnostics and call chains

Overview

// comptime(expr) — evaluate any pure expression at compile time
fixed int32:KB = comptime(1024);
fixed int32:MB = comptime(KB * 1024);

// comptime { ... } — run an entire block at compile time
comptime {
    fixed int32:check = 2 + 2;
};

// comptime func: — declare a CTFE-only function
comptime func:square = int32(int32:n) { pass n * n; };
fixed int32:nine = comptime(square(3));

Comptime differs from macros:

When to Use Comptime

• Compute lookup tables, constants, masks, bit-widths at build time
• Inspect types via @typeInfo, @sizeof, @fieldType
• Drive generic algorithms with T: type parameters
• Fail the build on invalid configurations (assert_static)

See also: META/NITPICK_COMPTIME/COMPTIME.md for the design tracker.