this post was submitted on 01 Sep 2023
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Programming

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What are your programming hot takes? (lemmy.ml)
submitted 1 year ago by 257m@lemmy.ml to c/programming@programming.dev
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[–] indepndnt@lemmy.world 2 points 1 year ago (3 children)

Honest question: is there a mapping function that handles the case where you need to loop through an iterable, and conditionally reference an item one or two steps ahead in the iterable?

[–] hellishharlot@programming.dev 2 points 1 year ago (1 children)

Not that I'm aware of but that's a condition where you're thinking with an index. What's the difference you're looking for?

[–] indepndnt@lemmy.world 1 points 1 year ago (1 children)

Something like parsing a string that could have command codes in it of varying length. So I guess the difference is, is this a 1-, 2-, or 3-character code?

I have something like this in a barcode generator and I keep trying to find a way to make it more elegant, but I keep coming back to index and offset as the simplest and most understandable approach.

[–] hellishharlot@programming.dev 1 points 1 year ago

So you could generate lists of 1, 2, and 3 character code items rather than looking at index +1 or something.

[–] drathvedro@lemm.ee 2 points 1 year ago

In js there's reduce. Something like

arr.reduce((result, currentValue, currentIndex, original) => {
if(currentIndex < original.length - 2
    && original[currentIndendex + 2] % 2 === 0 ) {
    result.push(currentValue / 2) 
} else { 
    result.push(currentValue);
}
return result;
}, [])

This would map arr and return halved values for elements for which the element two steps ahead is even. This should be available in languages where map is present. And sorry for possible typos, writing this on mobile.

[–] xigoi@lemmy.sdf.org 2 points 1 year ago* (last edited 1 year ago)

In Haskell, you could do something like map (\(thisItem, nextItem) -> …) (zip list (tail list))