June 19, 2009
9:12 p.m.
On 18 Jun 2009, at 21:19, Lie Ryan wrote:
In list/generator comprehension, currently we have no way to access the result of the expression and have to write something like this:
[f(x) for x in l if f(x) > 0]
if f() is heavy or non-pure (i.e. have side effects), calling f() twice might be undesirable.
Even if f() is not a function such as
[x + 1 for x in l if x + 1 > 0]
it looks ugly since we're repeating ourself.
We can work around it like this:
[y for y in (f(x) for x in l) if y > 0]
but then we have an unnecessary nested loop comprehension
You can write: [y for x in l for y in [f(x)] if y > 0] Which is even worse ;) -- Arnaud