Just guessing at the parent's intent, but the specification of a function can be decoupled from the production of an optimized implementation of that function,

Just guessing at the parent's intent, but the specification of a function can be decoupled from the production of an optimized implementation of that function, especially if the structure of the function is constrained in some way. This approach is used to some degree in producing, for example, optimized BLAS implementations and other similar routines: http://view.eecs.berkeley.edu/wiki/Autotuners http://view.eecs.berkeley.edu/wiki/Autotuners Of course, you do then need to juggle multiple languages. Different languages can be better at expressing different things, though (e.g., "what the function does" versus "how the function does it"), so it's not inherently crazy.