Here is a long and detailed post from Andy Wingo on how he improved numerical performance in the Guile language by carefully removing runtime type information ("unboxing"). "If Guile did native compilation, it would always be a win to unbox any integer operation, if only because you would avoid polymorphism or any other potential side exit. For bignums that are within the unboxable range, the considerations are similar to the floating-point case: allocation costs dominate, so unboxing is almost always a win, provided that you avoid double-boxing. Eliminating one allocation can pay off a lot of instruction dispatch."

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