#ctre
3 posts tagged #ctre.
Validating a string before the program exists
CTRE matches run inside constant expressions, so a regex can check and parse a string literal while the compiler is still working. A malformed version string then stops the build rather than surviving into production, and the parsed result is available as a constant.
The C++20 feature that gave CTRE its interface
Writing ctre::match<"[a-z]+"> requires a string literal to be a template argument, which C++20 allowed and every earlier standard did not. The older spelling still works and still compiles under C++17, so the two sit side by side and show exactly what the feature bought.
Measuring std::regex against a compile-time matcher
std::regex has a reputation, and reputations are worth checking. Measured at its most favourable, with the pattern compiled once outside the timed loop, it takes about seventy times longer per match than CTRE. Include the construction that real code usually pays for and the gap widens by another order of magnitude. Episode 1 of a series on compile-time regular expressions and the language features that make them possible.