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> But collecting values has nothing to do with iterating or looping. It should be a separate construct. I don't care about such rules. Personally I have no pr

• lisper 4y ago
  > I don't care about such rules. Yes, that is clear. > Personally I have no problem using: Loop is fine for simple examples like this. But I am currently maintaining a code base that has LOOPs with dozens and dozens -- sometimes a few hundred -- clauses. A single LOOP can extend over multiple pages. It's a nightmare. Note that LOOP can fail even for simple examples. Suppose I have a list of lists of numbers and I want to collect all the prime numbers. With WITH-COLLECTOR I can do this: (with-collector collect (dolist (l1 l) (dolist (n l1) (if (primep n) (collect n))))) But with LOOP I can't because there is no way for an inner loop to collect into a collector bound in an outer loop. I have to collect the individual sub-lists and then append them, or something like that, which is both inelegant and inefficient. And if I have a tree of items which I want to walk over and collect all of the once satisfying a predicate, LOOP just doesn't handle that at all. But by separating collection from iteration it becomes trivial: (with-collector collect (do-tree (item tree) (if (predicate item) (collect item)))) Neither WITH-COLLECTOR and DO-TREE are part of CL, of course, but writing them is an elementary exercise (and both are part of ergolib if you really don't want to be bothered).