On Dec 31, 8:49 am, Konrad Hinsen <konrad.hin...@laposte.net> wrote: > Suppose I write > > (defn foo [x] > (let [f (. Math log 0.5)] > (* f x))) > > Does the Clojure compiler calculate the constant expression (. Math > log 0.5) once, or at every function call?
Folding constants in nontrivial floating-point expressions is an aggressive optimization that can break some subtle code. For example, when building LAPACK, the file that tries to determine parameters of the floating-point units generally has to be compiled with no optimization. I'd much rather keep that part of the optimization turned off, or be very selective about when it gets turned on. Furthermore, in some cases (FFTs on the Cell processor is the modern example, if I recall correctly), it's better to recompute constants on the fly then to look them up in a table. mfh --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
