The math functions are statically inlined for performance. Wrapping them in another level of function/var will have a significant impact on performance even if assertions for preconditions are turned off.

Spec assertions (not pre/post checks) can actually be compiled completely out of production code so those can really be nothing (but not if you're adding them in wrapper layers).

spec is wholly independent of the pre/post conditions.

In this respect, they share the characteristic of being easy to wholly disable (i.e. prevent them from being compiled at all). With pre & post conditions if the var `clojure.core/assert` is bound to false, then they're elided. The usual pattern is to have them on for testing, and disable when compiling for production.