You can use an `and' pattern:
(: do-it (Thing -> String))
(define (do-it thing)
(match thing
((and p [Person fn ln])
(displayln fn)
(person-name p))))
Vincent
At Tue, 4 Dec 2012 17:53:57 -0500,
Ray Racine wrote:
>
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> How does one bind an identifier to the matched structure?
>
> In SML, Scala one can do something along the lines of s@S (x y z)
>
> #lang typed/racket
>
> (struct: Thing ())
> (struct: Person Thing ([fname : String] [lname : String]))
>
> (: person-name (Person -> String))
> (define (person-name p)
> (string-append (Person-lname p) ", " (Person-fname p)))
>
> (define js (Person "Joe" "Smith"))
>
> (: do-it (Thing -> String))
> (define (do-it thing)
> (match thing
> ([Person fn ln]
> (displayln fn)
> (person-name thing))))
>
> This fails as `thing' is not recognized as a Person.
>
> I guess I'm wondering if there is something along the lines of the
> following in `match'.
>
> (match thing
> (p@[Person fn ln]
> (person-name p)))) ;; p is typed as a Person
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>
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