In Rust when matching on Result or Option types I can return early from the function call with the return keyword. Is there an equivalent way to do that in Elm when matching Result or Maybe types?

[image] Philipp_Krueger: You can use Result.andThen or Maybe.andThen in function pipelines to achieve the same effect. Its probably worth illustrating this with an example. Lets suppose our error type is String and result type is Int, throughout some series of functions that we are going to p…

You can use Result.andThen or Maybe.andThen in function pipelines to achieve the same effect.

[image] stevensonmt: return early from the function call with the return keyword. Is there an equivalent way to do that in Elm Elm functions are a single expression that is evaluated to some value. They are not defined to evaluate in any particular order so the concept of ‘early’ isn’t meanin…

Rust’s option and result types already have .map and .andThen functions defined on them, so I’ll assume you’re familiar or have at least used them briefly. There is a fundamental difference between a language like Elm and a language like Rust; everything in Elm is an expression. There are no statem…

Thanks to everyone for the help. “andThen” really means “ifJustThen” or “ifOkThen”. I was worried about having to handle the error in the second and third functions in a pipeline.

Another name for “andThen” is “flatMap” (map, then flatten).

Leaving the original post below but I did finally figure this out, I think. Recursion is the secret. isIsogram : String -> Bool isIsogram sentence = recursiveCheck Set.empty sentence recursiveCheck : Set Char -> String -> Bool recursiveCheck set input = case String.uncons input of Nothing…

[image] stevensonmt: in the exercism Isogram problem, a naive solution is to take the input string, convert it to a set of chars and compare the size of the set with the length of the string Yes, that’s exactly how I’d do it. isIsogram string = string |> String.toList |> …

I don’t think there is anything wrong with that solution, but it is not the most efficient. Building the Set requires going over all characters twice – once to add each char to a list, and once to insert each char from the list into the set. For this problem that doesn’t matter because all the inpu…

I see! :+1: (Sorry, I didn’t realize your post above was edited. The new stuff above the ====== line.)

Early return from function on Err or Nothing

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Early return from function on Err or Nothing

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