You could use Haskell for prototyping your idea and call a, hopefully faster, C implementation for portions of your code. Having said that, you should always use a profiler to determine what portions of your code can potentially benefit from going lower level.
If you do a lot of matrix computations, for example, you can always call a fast Fortran library like Blas or Lapack through a C layer.
If you do a lot of matrix computations, for example, you can always call a fast Fortran library like Blas or Lapack through a C layer.