''Blitz++ is a CeePlusPlus class library for ScientificComputing'  

A 2005 version (0.9) is available from sourceforge: 
*** http://sourceforge.net/projects/blitz/files/

Blitz++ arrays offer functionality and efficiency competitive with Fortran 90, but without any language extensions. The Blitz++ library is able to parse and analyze array expressions at compile time, and performs loop transformations which have until now been the responsibility of optimizing compilers.
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This library is not currently under development. BoostuBlas offers an alternative and there is also a discussion there of the rationale for a choice.
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See ExpressionTemplate, MatrixTemplateLibrary, TemplatesForNumerics, StdValarray.
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CategoryCpp CategoryCppTemplates