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Parse, don't validate (2019)

(lexi-lambda.github.io)
398 points declanhaigh | 1 comments | 07 Mar 23 08:47 UTC | HN request time: 0.211s | source
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bruce343434 ◴[07 Mar 23 10:54 UTC] No.35053912[source]▶
Note that this basically requires your language to have ergonomic support for sum types, immutable "data classes", pattern matching.

The point is to parse the input into a structure which always upholds the predicates you care about so you don't end up continuously defensively programming in ifs and asserts.

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1. armchairhacker ◴[07 Mar 23 13:45 UTC] No.35055230[source]▶
I wish more languages had some equivalent of records, tagged unions, and pattern matching.

Don't have to be 100% immutable or perfect ADTs: see Rust, Swift, Kotlin. Even TypeScript can do this, albeit it's uglier with untagged unions and flow typing instead of pattern matching.