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?
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.
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.
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?
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?
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.
So you could generate lists of 1, 2, and 3 character code items rather than looking at index +1 or something.
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.
In Haskell, you could do something like
map (\(thisItem, nextItem) -> …) (zip list (tail list))