(JS/TS is my main language)
I love reduce()! It's a hammer/nail method for me. Everything looks like a problem solvable by reduce. (I'm often wrong on that, but I quite enjoy learning why by trying).
I really like taking the implementation away from the call site, so that the call site reads
const myNewValue = data.reduce(doSomethingMagic);
(and then `doSomethingMagic` is defined somewhere else). So simple.
I failed a job interview once by using reduce() in a coding test. The reviewer didn't understand why I hadn't used a loop. Loops are easier, for sure, but they sprawl and are open to hacking. They can bring in state from outside the loop. They make the call site long (you always have to read the implementation to learn that you don't need to read it). The same interviewer actively liked to have loop bodies modify the loop conditions (e.g. by taking items out of the source array and decrementing the end condition, so the loop would end earlier). That's the kind of "clever" I find unpredictable and hard to think about. Probably a good thing he rejected me.
> The same interviewer actively liked to have loop bodies modify the loop conditions (e.g. by taking items out of the source array and decrementing the end condition, so the loop would end earlier).
Wow. That is the kind of monkey business that would have me running for the exits. Yikes.
IIRC both Dijkstra and Knuth used this approach extensively, instead of "if (some_cond) break;" — partly because the latter was not yet invented, partly because of their reliance on explicitly stated and documented right in the code loop invariants.
That's fair. Let me modify my statement: If the person doing this was over 50 and had developed this habit in old languages where that was basically idiomatic, it wouldn't scandalize me - though I'd raise an eyebrow to see it in a modern language.
But if someone's 28 and doing that stuff in Python or JavaScript, they're a bit of a loon, imho.
the_other · · focus · HN ↗
I really like taking the implementation away from the call site, so that the call site reads
(and then `doSomethingMagic` is defined somewhere else). So simple.I failed a job interview once by using reduce() in a coding test. The reviewer didn't understand why I hadn't used a loop. Loops are easier, for sure, but they sprawl and are open to hacking. They can bring in state from outside the loop. They make the call site long (you always have to read the implementation to learn that you don't need to read it). The same interviewer actively liked to have loop bodies modify the loop conditions (e.g. by taking items out of the source array and decrementing the end condition, so the loop would end earlier). That's the kind of "clever" I find unpredictable and hard to think about. Probably a good thing he rejected me.
xp84 · · focus · HN ↗
Wow. That is the kind of monkey business that would have me running for the exits. Yikes.
Joker_vD · · focus · HN ↗
xp84 · · focus · HN ↗
But if someone's 28 and doing that stuff in Python or JavaScript, they're a bit of a loon, imho.