Can a range-based for-loop be used with a constant integer value (C++11)

Question

So my question is simply, can something like this work:

int size = 100;
for(int i : size)
  // bla

And if not, could you briefly explain why?

No, what would you expect this to do? An `int` is not a collection... (specifically, it has no `begin()` and `end()` member functions, which would be the requirement for range-based for loops to work.) — The Paramagnetic Croissant, Nov 07 '14 at 14:43
Perhaps you want something like http://stackoverflow.com/questions/7185437/is-there-a-range-class-in-c11-for-use-with-range-based-for-loops ? — Nate Kohl, Nov 07 '14 at 14:46

score 2 · Answer 1 · answered Nov 07 '14 at 14:45

No, that does not work. A number is not a range. How would you define begin(100) or end(100) (which is what the range-based for loop calls internally)?

My guess is you'd want this as a shorthand for a loop from 0 to 99. But why not one from -2147483648 (or whatever std::numeric_limits<int>::min() is on your implementation) to 99?

score 1 · Answer 2 · answered Nov 07 '14 at 14:46

No this will not work!

Range-based loop works only on collections, which int is not.

Moreover, if you are comparing it with a normalfor loop, where is the initialization (i=0) statement and comparison (i<size) statement for i? The construct does not tell when to start the loop and when to end!

score 1 · Accepted Answer · answered Nov 07 '14 at 14:47

No. Range-based for-loop are introduced for iterating through a collection, not some arbitrary range. Running a loop for a range of values can be achieved by using for, while or do-while. If you need such loop, for regular activities, that can be implemented by simply wring a function, a macro, that may take a function, functor, or lambda.

Can a range-based for-loop be used with a constant integer value (C++11)

3 Answers3