Better name needed for applying a function on elements of a container

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+6 Q:

Better name needed for applying a function on elements of a container

I have a container class (containing a multi-index container) for which I have a public "foreach" member-function, so users can pass a functor to apply on all elements.
While implementing, I had a case where the functor should only be applied to some elements of a range in the container, so I overloaded the foreach, to pass some valid range.
Now, in some cases, it was worthwhile to stop on a certain condition, so practically, I let the foreach stop based on the return-value of the function.

I'm pleased with how the system works, but I have one concern:
How should a "foreach" on a range, with stop conditions be called?
Anyone knows a generic, clear and concise name?

a generic name? ConditionalIterator? RangeIterator? Or since it's a function, perhaps IterateRange?

David Hedlund 2010-05-26 09:06:19

How about find_if(...), as in stl ?

Viktor Sehr 2010-05-26 09:06:33

+2 A:

Maybe until or something?

Andreas Brinck 2010-05-26 09:07:06

+6 A:

Based on your description, i'd go for apply_until().

Georg Fritzsche 2010-05-26 09:10:02

I like the apply_... name because it shows that it is an interface to apply functions. Strangely enough, I put it in the the title, but it hasn't crossed my mind to actually use it as a function name. I guess, foreach was stuck too much in my head.

stefaanv 2010-05-26 09:17:31

+1 A:

I'd probably call it either foreach_until or foreach_while (attempting to follow a convention based on the _if functions like replace_if and remove_if, except that the condition here isn't "if" each one is true, it's "until" the end condition holds). Or just foreach. std::for_each ignores the return value of the functor, but that doesn't necessarily mean that your function called foreach has to. I think it's a pretty common idiom for a callback function to have a return value allowing early exit from the controlling loop.

If the callback returns either a false value (to continue) or a true value (to halt), then you could call the function find_if. That's basically what it is, and it could be implemented using std::find_if, even if the caller isn't interested in which iterator provoked the end condition.

Steve Jessop 2010-05-26 10:29:51

I am intrigued by the find_if, because it is answered twice. I thought that "find..."-functions are about returning members and that "..._if" functions used "predicates" as in "pure functions that return a boolean based on some condition". Am I being too strict?

stefaanv 2010-05-26 11:08:47

Predicates return a value "testable as true", not necessarily a boolean. They aren't required to be pure, but they must not call non-const functions on their parameter: I neglected to mention that as a condition. All in 25/7. You're right that `find` functions are about returning the iterator that triggered the "stop", but you can always ignore a return value. Really I just mean that if `find_if` is "close enough" to what you want, then use it even if conceptually you aren't finding anything. If it's not "close enough", don't use that name :-)

Steve Jessop 2010-05-26 16:14:17

+1 A:

If you can provide a subset function that returns a view of the elements of interest, maybe you don't need apply_until(). Just myContainer.subset(3, 17).foreach(myFunctor) I think that's a better separation of concerns.

Carl Manaster 2010-05-26 13:20:53

Wow, a sort of different approach. It sounds nice. Practically for me, it would mean having another class (the subset) with access to the internal container, though.

stefaanv 2010-05-26 13:59:12

On second thought, it would only need 2 iterators, so I should keep this in mind

stefaanv 2010-05-26 14:06:12

ansaurus

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Better name needed for applying a function on elements of a container

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