[plt-scheme] Renaming of contract names

--- Jens Axel Søgaard <jensaxel at soegaard.net> wrote:

> Hi all,
> 
> I working on random access lists. I'd like to implement all
> operations from srfi 1 including "any". Since (lib "contract.ss")
> contains a contract called "any", I tried  renaming it on import:
> 
> (module a-module mzscheme
>    (require (all-except (lib "contract.ss") any)
>             (rename (lib "contract.ss") obj? any))
> 
>    (provide/contract
>     [empty? (obj? . -> . boolean?)])
> 
>    (define empty? null?)
> 
>    (define (any pred xs)
>      (cond [(null? xs) #f]
>            [(pred (car xs)) #t]
>            [else            (any (cdr xs))]))
> 
>    (display (any even? (list 1 2 3 4 5 6)))
>    (newline))
> 
> But nevertheless I get the error:
> 
>     any: Use any out of an arrow contract in: obj?
> 
> Is this supposed to happen?

I think 'any' (and thus, 'obj?' here) is only allowed on the
right-hand side of arrow contracts. Contracts such as
  (list? . -> . obj?)
seem to be fine.

Ryan

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