Hacker News new | past | comments | ask | show | jobs | submit
jiehong | on: Anecdotally, programmers dislike "reduce"
> … to call them Select and Where.

While map is a great name, I always struggle to remember if ‘filter’ keeps elements that match the condition or removes them.

I mean, it’s like a colander: you filter noodles and water, but which one do you keep? The noodles, right? But, replace noodles with tea and now you want to keep the water part.

Naming is hard I guess.

saghm | parent | next
There's always the Ruby strategy of just making all the names work. `select` and `filter` are buddies and you can use whichever you want or even go back and forth. Not a fan of `reduce`? That's fine, `inject` has got your back. Miss getting to type `collect` from Java or Rust? Don't worry, just use it instead of `map`, it's the same thing.
loading story #49737299
reddit_clone | parent | next
Talking about un-guessable, misleading function names,

C++ std::remove.

I would never have guessed what it does exactly. (It moves elements that match the filter to the front, and moves the end-marker forward. Leaves all the elements in the collection. You need to erase them yourself. )

loading story #49734658
loading story #49734671
seanw444 | parent | next
I've never run into a generic "filter" function which keeps only the non-matching elements.
loading story #49734842
dreamcompiler | root | parent
Common Lisp's filter is remove-if which works this way.

(It also has remove-if-not but that's deprecated and if you use it your code smells.)

rmunn | parent | next
The filter keeps the tea... it's just that you then lift the filter out of the cup, carrying the tea with it. Flip your brain around to see it from that direction and it might help you with the mnemonics.
| parent | next
{"deleted":true,"id":49735392,"parent":49733452,"time":1789609021,"type":"comment"}
andrekandre | parent | next

  > I always struggle to remember if ‘filter’ keeps elements that match the condition or removes them
if you had parameter names maybe it might help?

`filter(where:)` like in swift...?

loading story #49734327
pavlov | parent | next
Maybe those two could be filter_for (the “where” case) and filter_out.
listenallyall | root | parent
Kotlin has filter and filterNot (it also has separate "reduce" and "fold" functions, dependingon whether you want to specify an initial accumulator value or not)
dcminter | parent | next
If you're making tea with a colander something is very wrong ;)
SamBam | root | parent | next
I was thinking an apt analogy might be making stock -- you filter out all the solid food you don't want to keep in the liquid.

And it's a doubly-good analogy, because I have occasionally gotten that confused in real-life as well. Twice in the past ten years I've had a stock boil away for three hours, and then set a colander in the sink and poured it through, only to watch my beautiful stock swirl down the drain because motor-memory made me forget that I wasn't draining pasta but should have put the colander in a bowl...

NooneAtAll3 | root | parent
depends on the size of the sieve, but sometimes one does cook a whole stewpot of tea at once (f.e. in canteen)
thaumasiotes | parent | next
> While map is a great name, I always struggle to remember if ‘filter’ keeps elements that match the condition or removes them.

In Common Lisp both functions exist, under the names `remove-if` and `remove-if-not`.