To add a bit to what Alexis said about flat contracts: On Wed, May 22, 2019 at 1:23 PM Alexis King <[email protected]> wrote:
> Your intuition is right, but let me make it more precise: foo? is used > when something is a flat contract, and foo/c is used otherwise. Flat > contracts only check *first order properties* of values, which is a > technical term that captures what you mean by “general nature.” > > The important distinction is that first order properties can be checked > immediately … Since flat contracts only perform first-order checks, a flat > contract can be used as a predicate, so you can write (foo? x) to get back > a boolean. Likewise, all predicates can be used as flat contracts. > Some flat contracts use the foo/c naming convention when they include special error reporting, which can potentially involve a performance cost beyond a simple predicate. For example, the `xml` module provides both `xexpr?` and `xexpr/c`: https://docs.racket-lang.org/xml/index.html#(def._((lib._xml%2Fprivate%2Fxexpr-core..rkt)._xexpr%2Fc)) I write a lot of these kinds of contracts, and I think they're very effective. In my RacketCon talk last year, I discussed using contracts to do XML validation and produce error messages good enough for non-programmers to fix invalid XML files: https://youtu.be/pv0lLciMI24?t=5479 -Philip -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAH3z3gYGGmxaNGJgVFG8y%3Dum2whn-LBj9-Q2vOHeem_cvANzAg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
