Le mardi 20 août 2013 07:48:37 UTC+2, Steven D'Aprano a écrit : > On Mon, 19 Aug 2013 22:34:00 +0200, Antoon Pardon wrote: > > > > > Op 19-08-13 19:05, Steven D'Aprano schreef: > > > > > > > > >> I wish Python had stronger support for enforcing constantness, to whit, > > >> some way to say "you can't rebind or delete this name once it is > > >> bound". You can do it with attributes, by use of property, or in C > > >> extensions, but you cannot do it with top-level name bindings. It makes > > >> me terribly sad that you can do this: > > >> > > >> import math > > >> math.pi = 3.0 > > >> > > >> > > >> although I can't decide whether I am less sad or more sad to see that > > >> the behaviour of math.sin and friends doesn't depend on math.pi. > > > > > > Why should you expect math.sin and friends be dependant on math.pi? > > > AfAIR the numerical algorithms for calulating sin and friends don't > > > depend on (the value of) pi. So there is no reason to suspect that > > > altering math.pi would have any effect on the results of these > > > functions. > > > > > > Of course they depend on pi. Or rather, they depend on the geometric > > properties of circles, which are related to pi. If the ratio of the > > circumference of a circle to its diameter was exactly 3, instead of > > 3.1415..., then sine and cosine functions would be periodic with period 6 > > rather than τ = 2π. > > > > If you consider the implementation of sin and cos functions, they usually > > reduce the argument modulo π to something in the first quadrant, and then > > use symmetry to adjust the value. So changing the value of pi could, in > > principle, change the implementation of sin, cos and tan. > > > > > > -- > > Steven
--------- Never heard about series, Taylor, Maclaurin, ... ? jmf -- http://mail.python.org/mailman/listinfo/python-list
