Template Metaprogramming Techniques

CeePlusPlus techniques that yield compile time solutions for problems usually determined at runtime:

• the unrolling of a loop
• function calculations (cos, sin, ...)
• presence of member functions for a given object

Implementations:

• Alexandrescu's Loki
  • http://loki-lib.sourceforge.net/
• TinyTTL
• Boost MPL
  • http://www.boost.org/libs/mpl/doc/index.html

Template metaprogramming stores information used for compile time calculations in the type system. Partial template specicialization handles special cases. Metaprograms use metafunctions and metavariables:

• TemplateMetavariables
• TemplateMetafunctionIdentity
• TemplateMetafunctionIf
• TemplateMetafunctionAnd
• TemplateMetafunctionHasFunction

Interestingly, the C++ standard allows escaping template closures and HigherOrder? templates. This makes compiling a small LambdaCalculus -like language to C++ Templates nearly trivial. Unfortunately, the standard-prescribed maximal recursion depth is rather low (13 levels, I believe), but most compilers have a much larger limit, usually in the range of several hundred levels.

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CategoryCppTemplates CategoryMetaprogramming