> combinations of .map, .filter, .reduce, etc are often less readable than doing the same thing in a nested loop. I often find map/reduce/filter easier to read

> combinations of .map, .filter, .reduce, etc are often less readable than doing the same thing in a nested loop. I often find map/reduce/filter easier to read when using named functions (or lazy data structures ) for intermediary results - depending on the language/runtime that might imply more allocations - or not. Eg pseudocode: Integers.filter(//non-obvious prime sieve).sum() Vs Primes = Integer.filter(//non-obvious prime sieve) Primes.sum() Or lifting the anonymous filter to primes()-filter: Integers.primes().sum()