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C++ Language/Templates/Metaprogramming/NumericTemplateParameters
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
A template-parameter usually serves as a placeholder for a type.
But, a template-parameter could be numeric.
This gives templates a capability of performing compile-time calculations by "template-metaprograms".
Additional information about numeric template-parameters (includes interactive examples)