Jon Harrop <j...@ffconsultancy.com> writes: > You mean people use that pattern as a fast alternative in languages where > user-defined functions are very slow, like Python and Mathematica?
It really doesn't matter whether the language is fast or slow--there are going to be applications where calling the comparison function multiple times per element is slower than calling it once per element and storing the result. Note the Haskell idiom (sortBy (compare`on`f) xs) is similar to DSU but calls the comparison function multiple times. Python 3.0 went overboard by actually removing the cmp argument and requiring use of the key argument. That requires various kludges if the key is, say, a tree structure that has to be recursively compared with another such structure. Maybe then can bring back cmp someday. -- http://mail.python.org/mailman/listinfo/python-list
