Comptime Metaprogramming

Auto's compile-time execution engine allows you to run code during compilation, enabling powerful metaprogramming without traditional macros.

What is Comptime?

The comptime keyword marks code that runs at compile time rather than runtime. This allows you to:

• Generate code programmatically
• Validate invariants before the program runs
• Compute constants from complex expressions
• Configure behavior based on compile-time parameters

Examples

comptime fn generate_table(size: int) -> [int] {
    var table: [int; size]
    for i in 0..size {
        table[i] = i * i
    }
    return table
}

const squares = generate_table(16)

Compared to Macros

Unlike C macros or Rust's macro_rules!, comptime code is:

• Type-safe
• Debuggable
• Written in the same language as runtime code
• Capable of accessing the full compiler API