Alex Martelli wrote: > When teaching some programming to total newbies, a common frustration > is how to explain why a==b is False when a and b are floats computed > by different routes which ``should'' give the same results (if > arithmetic had infinite precision). Decimals can help, but another > approach I've found useful is embodied in Numeric.allclose(a,b) -- > which returns True if all items of the arrays are ``close'' (equal to > within certain absolute and relative tolerances): > > >>> (1.0/3.0)==(0.1/0.3) > False > >>> Numeric.allclose(1.0/3.0, 0.1/0.3) > 1 > > But pulling in the whole of Numeric just to have that one handy > function is often overkill. So I was wondering if module math (and > perhaps by symmetry module cmath, too) shouldn't grow a function > 'areclose' (calling it just 'close' seems likely to engender > confusion, since 'close' is more often used as a verb than as an > adjective; maybe some other name would work better, e.g. > 'almost_equal') taking two float arguments and optional tolerances > and using roughly the same specs as Numeric, e.g.: > > def areclose(x,y,rtol=1.e-5,atol=1.e-8): > return abs(x-y)<atol+rtol*abs(y) > > What do y'all think...?
atol sounds suspicious to me, but otherwise fine. Georg _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
