Andrea Fontana:
Not funny btw :) It's not so easy to find out. And it's not
easy to write a "cached map" function if you use classes or
some pointers as ElementType...
Not caching _input.front in filter() means that filter() assumes
the front() of its argument range to act as a pure function (even
if this isn't enforced by the type system). At least this should
be documented in std.algorithm ddocs...
Python filter() does not work that way:
from sys import stdout
def fun(x):
stdout.write("*")
return x
list(filter(lambda x: True, map(fun, xrange(5))))
Prints:
*****
Bye,
bearophile
