Mark Engelberg a écrit : > So one thing I don't get is why would tristan's pow code sometimes > generate a BigInteger, and sometimes a Long for the same resulting > number? > Good question.
(pow 2 32); returns 4294967296 (BigInteger) (pow 4 16); returns 4294967296 (Long) (pow 16 8); returns 4294967296 (Long) and if we expand Tristan's pow we get: (* 2 (pow 2 31)); where (class (pow 2 31)) is Long since Integer/MAX_VALUE is 2^31-1 (* 4 (pow 4 15)); where (class (pow 4 15)) is Integer (* 16 (pow 16 7)); where (class (pow 16 7)) is Integer ;(2, 4 and 16 are Integers). With (* 4 (pow 4 15)) or (* 16 (pow 16 7)) each operand is promoted from Integer to Long and since the result can't fit into an Integer, a Long is returned. With (* 2 (pow 2 31)) each operand is promoted to BigInteger (since (pow 2 31) is already a Long) and... the result is not reduced to a Long albeit small enough. Looking at Numbers.java, the code that should perform this reduction is commented http://code.google.com/p/clojure/source/browse/trunk/src/jvm/clojure/lang/Numbers.java#270 and is commented since it first appeared in rev 811. We'll have to wait for Rich to know why these two lines are commented out. Christophe --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
