In article <559a2ee3-fb2c-477f-a444-7edbb6da8...@r1g2000yqj.googlegroups.com>, Patrick Maupin <pmau...@gmail.com> wrote: >On Mar 29, 10:29=A0pm, Steven D'Aprano ><ste...@remove.this.cybersource.com.au> wrote: >> On Mon, 29 Mar 2010 19:24:42 -0700, Patrick Maupin wrote: >> > On Mar 29, 6:19=A0pm, Steven D'Aprano <st...@remove-this- >> > cybersource.com.au> wrote: >> >> How does the existence of math.fsum contradict the existence of sum? >> >> > You're exceptionally good at (probably deliberately) mis-interpreting >> > what people write. >> >> I cannot read your mind, I can only interpret the words you choose to >> write. You said >> >> [quote] >> See, I think the very existence of math.fsum() already violates "there >> should be one obvious way to do it." >> [end quote] >> >> If sum satisfies the existence of one obvious way, how does math.fsum >> violate it? sum exists, and is obvious, regardless of whatever other >> solutions exist as well. > >Because sum() is the obvious way to sum floats; now the existence of >math.fsum() means there are TWO obvious ways to sum floats. Is that >really that hard to understand? How can you misconstrue this so badly >that you write something that can be (easily) interpreted to mean that >you think that I think that once math.fsum() exists, sum() doesn't >even exist any more????
To a mathematician sum(set) suggest that the order of summation doesn't matter. (So I wouldn't use sum for concatenating lists.) Harshly, sum() should be used only for operator + both associative and commutative. Now for floating point numbers the order of summation is crucial, not commutative (a+b)+c <> a+(b+c). So the obvious thing for someone versed in numerical computing do is looking whether sum() gives any guarantees for order and whether there may be a special sum() for floating point. (This is not very realistic, because such a person would have skimmed the math library a long time ago, but anyway.) Met vriendelijke groeten, Albert van der Horst -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- like all pyramid schemes -- ultimately falters. alb...@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst -- -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. alb...@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst -- http://mail.python.org/mailman/listinfo/python-list
