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What are the benefits of using `and` instead of `&&` when defining concepts?

January 29, 2023

I found that some CppCon speakers used and instead of && to define concepts and used && in "normal" boolean expressions, but I can’t figure out the benefits of doing so.

The only material about naming convensions of concepts that I can found is P1851: Guidelines For snake_case Concept Naming, but it says nothing about this.

Can anyone tell me why?

Example:

template <typename T>
concept boolean_testable
    = std::convertible_to<T, bool>
      and requires(T&& t) {
            { !std::forward<T>(t) } -> std::convertible_to<bool>;
          };

Instead of:

template <typename T>
concept boolean_testable
    = std::convertible_to<T, bool>
      && requires(T&& t) {
           { !std::forward<T>(t) } -> std::convertible_to<bool>;
         };

>Solution :

There is absolutely no difference between && and and. As tokens they behave identically in all respects expect that the preprocessor # stringify operator respects their different spelling.

For example you can even replace T&& with T and and the code will still have identical meaning.

This is purely a style choice.

See [lex.digraph].