Embracing User-Defined Literals Safely

By Pablo Halpern

A fundamental design goal of C++ is to minimize the expressive differences between built-in types and user-defined types (UDTs). Just as we can overload operator+ for our UDT, we can also specify a syntax for creating a value of that type; think 123_bigint or "[a-z]*"_regexp. But just because we can overload an operator or create a user-defined literal (UDL), doesn’t mean that we should do so. In this talk, we will cover the benefits of UDLS, several ways of defining them (each more powerful and complex than the one before), some best practices, and — most importantly — the pitfalls of defining one’s own UDLs and when not to.