[racket] Why this contract violation behaviour?

First cut: Contracts check cross-module invariants. That's why they establish boundaries:

 http://doc.racket-lang.org/guide/contract-boundaries.html?q=contracts

When a module M provides a function f with a contract, calls w/i M to f are not checked. 

Second cut: if you know about contract regions, you can break modules into several contract regions and thus force contract checks within a module. 



On Nov 16, 2012, at 6:59 PM, Harry Spier wrote:

> Dear list members,
> 
> Can someone explain why in the following cases only two out of the three cases and not all of them cause a contract violation.
> Thanks,
> Harry Spier
> 
> #lang racket
> (provide/contract (amount positive?))
> (define amount -7)
> >
> contract
> promised: positive?
> produced: -7
> in: positive?
> contract from: anonymous-module
> blaming: anonymous-module
> 
> BUT--------------------------------------
> 
> #lang racket
> (provide/contract [amount (-> positive?)])
> (define (amount) -7)
> (amount)
> >
> No contract violation
> 
> AND-------------------------------------------
> 
> #lang racket
> 
> (provide/contract [amount (-> positive?)])
> (define (amount) -7)
> 
> (module* main racket
> (require (submod ".."))
> (amount))
> 
> >
> amount: broke its contract
> promised: positive?
> produced: -7
> in: the range of
> (-> positive?)
> contract from: 
> c:\users\harry\ocr_project\contract-test.rkt
> blaming: 
> c:\users\harry\ocr_project\contract-test.rkt
> at: c:\users\harry\ocr_project\contract-test.rkt:3.20
> ____________________
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>  http://lists.racket-lang.org/users

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