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Java, Lisp, etc. have multiple implementations too. Different implementations often have different characteristics -- performance, compliance with the standard,

• gohrt 13y ago
  Every Java implementation is compliant with the standard -- it is part of the "Java(TM)" trademark licensing.
  • pjmlp 13y ago
    In theory yes. But as any developer that deployed applications across multiple JVMs will tell you, there are a few surprises along the way.
• microtherion 13y ago
  In the specific case of C++, standard compliance was probably a pretty major factor, as the standard library for C++ is very complex, and vendors are not necessarily always fast to keep up with new features (or willing to port these to older platforms). For quite some time, STLport <http://www.stlport.org> http://www.stlport.org> was a life saver for providing modern, efficiently implemented library features on not-so-modern platforms. Conversely, the fact that the Apache library hadn’t been updated since 2008 probably means is that it’s not C++11 compliant at all, significantly behind most vendor libraries, and the effort for upgrading would be fairly significant.