Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

See here for more information about String Generators.

Expression	Attribute	Description
`str`	`Unused`	Generate `str`
`lit(str)`	`Unused`	Generate `str`
`string`	`Str`	Generate string supplied as the attribute
`string(str)`	`Str`	Generate `str`, if an attribute is supplied it must match