[fvdessen]

I had the opposite experience. We had a large client application that was too slow, with no obvious bottleneck on the flame graph. I replaced all the functional iterators by for loops among other similar optimisations, and improved the performance by a factor of 50. If you use programming constructs that are 50 times slower on average, your program will be 50 times slower on average.

[GordonS]

> If you use programming constructs that are 50 times slower on average, your program will be 50 times slower on average

Well, yes, but the relative difference between a for and foreach loop is miniscule - not 50x difference. In absolute terms, the overhead of both is barely measurable, and is extremely unlikely to be a bottleneck in any client-side application.