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Format
The format library provides a class for formatting arguments according to a format-string, as does printf, but with two major differences: format sends the arguments to an internal stream, and so is entirely type-safe and naturally supports all user-defined types; the ellipsis (...) can not be used correctly in the strongly typed context of format, and thus the function call with arbitrary arguments is replaced by successive calls to an argument feeding operator%.
Iostreams
Boost.IOStreams provides a framework for defining streams, stream buffers and i/o filters.
Lexical Cast
General literal text conversions, such as an int represented a string, or vice-versa.
C++ 03