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Parse, Don't Validate (2019)

(lexi-lambda.github.io)
389 points melse | 1 comments | 26 Jun 21 07:23 UTC | HN request time: 0.542s | source
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wodenokoto ◴[26 Jun 21 09:11 UTC] No.27640366[source]▶
When I think of validation I think of receiving a data file and checking that all rows and columns are correct and generating a report about all the problems.

Does my thing have a different name? Where can I read up on how to do that best?

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quickthrower2 ◴[26 Jun 21 10:07 UTC] No.27640640[source]▶
I thought of input validation for web forms. Similar thing I guess. In Haskell you can create a type that you know is a validated email address but you still need a validation function from String -> Maybe Email to actually validate it at runtime
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1. WJW ◴[26 Jun 21 11:32 UTC] No.27641008[source]▶
I think for the usecase GP gives it'd be even better to have a function `String -> Either (LineNumber,String,[Problem]) Email`, so that you can report back which of the lines had problems and what kind of problems. For web form validation you can skip the line number but it'd still be useful to keep the list of problems, so that you can report back to the user what about their input did not conform to expectations.