> Why does list? allow a vector in the following contract? Contract in `provide' is used only when you `require' your module from other. If you want always test it, use define/contract
> Also, how do I indicate an optional (in this case keyword) argument? http://docs.racket-lang.org/reference/function-contracts.html#%28form._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._-~3e%2A%29%29 (->* (list? exact-nonnegative-integer?) (#:splice boolean?) any) Tue, 19 Aug 2014 22:44:57 -0700 от Kevin Forchione <[email protected]>: >Hi guys, >In an attempt to tighten up my code I started using the raise-xxxx-error >feature and then began looking at contracts. I like the concept and think it >would lead to cleaner looking code But I have two questions: > >Why does list? allow a vector in the following contract? Also, how do I >indicate an optional (in this case keyword) argument? > >(I’m assuming I’d have to define a contract to handle the valid >exact-nonnegative-integer/range for the index, unless there is one already >defined. I’ll have a go at that later. ) > >#lang racket > >(provide (contract-out > (insert-at (list? exact-nonnegative-integer? any/c . -> . any)))) > >(define (insert-at lst index val #:splice (splice #f)) > #;(unless (list? lst) > (raise-argument-error 'insert-at "list?" lst)) > #;(uqnless (exact-nonnegative-integer? index) > (raise-argument-error 'insert-at "exact-nonnegative-integer?" index)) > #;(unless (<= index (length lst)) > (raise-range-error 'insert-at "list" "" index lst 0 (length lst))) > #;(unless (boolean? splice) > (raise-argument-error 'insert-at "boolean?" splice)) > > (define-values (head tail) (split-at lst index)) > (append head > (cond > [(and splice (cons? val)) val] > [else (list val)]) > tail)) > >>(insert-at #(a b) 0 ‘c) >'(c . #(a b)) > >Thanks! > >-Kevin > > >____________________ > Racket Users list: > http://lists.racket-lang.org/users -- Roman Klochkov
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