Ask HN: Encyclopedia of discrete approximations, with reference implementations?

What does the community feel is the best reference out there for discrete approximations, preferably with reference implementations, the more comprehensive the better?

An ideal format would be the traditional name of the formula or number being approximated, a list of other common names for said formula/number, a list of "areas of applicability", a list of approximations annotated with computational efficiency, convergence info if applicable, reference implementations and hints for how best each approximation should be used, and finally a list of related formulas/numbers.

I recognize that a lot of this is on Wikipedia, but I'm looking for a dedicated resource that's a bit more cohesive.

Print resources are fine, but I'd love to find a good digital resource for this.