C/C++ is the language of choice for scientific and massively parallel programming. as far as I know Haskell is not really competitive in that area.
Linus Torvalds would disagree that C and C++ are the same language as suggested by "C/C++" and by the singular pronoun that follows.
http://harmful.cat-v.org/software/c++/linus
And maybe too much weight is given to Torvalds' views on this and other topics.
One can easily program as if it were C, using templates to avoid ugly macro mess for generic algorithms and types.
Edit: corrected is -> as.
Did you mean "as if"? If so, that's exactly what Torvalds objects to -- the things about C++ that supposedly represent improvements over C. He goes on about how many of the conveniences of C++ -- like the STL -- aren't as wrung out as most people think and don't actually work as intended.
I don't necessarily agree with his position in all respects, but some of the enhancements in C++, aren't actually enhancements.