> An off by one error may go harmlessly unnoticed at worst, or trigger a harmless segmentation fault at best, in which case it's very easy to find and fix the s

> An off by one error may go harmlessly unnoticed at worst, or trigger a harmless segmentation fault at best, in which case it's very easy to find and fix the silly problem Yes, but even better if you don't write the bug to begin with. It can also fail harmfully, like failing to trigger a segfault but producing the wrong computation, resulting in sending the wrong amount of energy to the X-Ray machine, the wrong amount of money in a bank operation, firing the wrong number of missiles, etc. > code that hides things tends to be much harder to debug, when it invariably fails In the general case, I agree. In the case of foreach loops (or maps or folds) the good thing is that they are well understood abstractions, not something your fellow coworker wrote and that you must understand from scratch. They are common idioms, just like you don't debug (under normal conditions) how a for-loop with an index works internally.