[Issue 12272] and(), or(), xor() to compose predicates

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=12272



--- Comment #3 from bearophile_hugs at eml.cc 2014-02-28 06:18:45 PST ---
(In reply to comment #2)

> Lambdas make this pretty easy...
> 
> names.filter!(s => s.startsWithJ && s.fourLetterLong)
> 
> Slightly longer, but _much_ more flexible.

With those templates you can define a new predicate in point-free style
(std.functional.compose!() does something similar for arbitrary functions):

alias two = and!(startsWithJ, fourLetterLong);

With lambdas it becomes similar to:

enum two = (in string s) => s.startsWithJ && s.fourLetterLong;

So are you suggesting to close down this ER because it's not useful enough?

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