[Docs] Add section on custom propositions #1345
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I proposed a suggestion at micahcantor#1. |
doc: refine custom propositions section
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Looks good, I think adding that example makes it more clear why we would need to add the proposition |
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capfredf
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Nov 6, 2023
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Thanks! |
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Section 5.2 of the guide describes how Typed Racket narrows types with propositions. However, I don't think this section makes it clear if and how users can define their own propositions from predicates. In 5.2, the proposition for the built-in type predicate
string?is discussed. Then, in 5.2.1, it jumps to defining custom one-sided propositions, a slightly more advanced concept. I think it could use a section in between that makes it explicit how to create a proposition from a predicate.Personally, I ran into this issue when I was learning Typed Racket: at the time I didn't understand from the guide how to define my own proposition. I asked a question on StackOverflow and got an answer, but I think this would be more clear with an example in the guide.
This PR adds such an example. I was a bit confused on whether to use
@examplesor@racketblockso I chose the latter which seemed simpler, but feel free to recommend changes to that, to the writing, or more generally to the structure/position of this section.