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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: 0.456s | 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. ocharles ◴[07 Mar 23 12:03 UTC] No.35054386[source]▶
This isn't strictly true, an alternative is to have a language with enough encapsulation that you can parse into something that can only be observed as correct. The underlying parsing doesn't have to parse into sum types, provided your observation functions always preserve the parsed invariants.