Preconditions

C++26 proposal adds native pre/post contract syntax to functions

A technical walkthrough demonstrates how C++26 introduces built-in 'contracts' syntax, letting developers express function preconditions directly in a function's signature using pre(...), rather than relying on assert() calls buried inside the implementation. The example shows a get_value function checking that an index is within a vector's bounds, with the condition visible in both declaration and definition.