[kccqzy]

Readability is subjective. I personally find fold almost always more readable than a for loop when the accumulator variable has a simple type. This is because merely seeing fold can already telling me several things: it will iterate over the entire collection without early exits like "break" in a loop; the data dependency between each iteration is made clear into a single variable.

I find it slightly difficult to read when the accumulator variable actually has multiple parts, like a complicated tuple. It's worse when part of the accumulator is a bool indicating whether it's finished; that's just a poor emulation of "break" in a for loop.