Could we please use the language of assertions here? We have worked hard to get people to see contracts as special boundary-associated assertions. And it's not clear whether we are succeeding. But if we don't use language properly, nobody will.
On May 30, 2014, at 10:06 PM, ro...@racket-lang.org wrote: > robby has updated `master' from 2eef2ce409 to ddb7477494. > http://git.racket-lang.org/plt/2eef2ce409..ddb7477494 > > =====[ One Commit ]===================================================== > Directory summary: > 70.1% pkgs/racket-pkgs/racket-doc/scribblings/reference/ > 25.1% racket/collects/racket/contract/private/ > 4.7% racket/collects/racket/contract/ > > ~~~~~~~~~~ > > ddb7477 Robby Findler <ro...@racket-lang.org> 2014-05-30 21:01 > : > | added invariant-contract > | > | Jay implemented this > : > M racket/collects/racket/contract/private/base.rkt | 15 ++++++-- > M racket/collects/racket/contract/region.rkt | 3 +- > M .../scribblings/reference/contracts.scrbl | 38 ++++++++++++++++++-- > > =====[ Overall Diff ]=================================================== > > pkgs/racket-pkgs/racket-doc/scribblings/reference/contracts.scrbl > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > --- OLD/pkgs/racket-pkgs/racket-doc/scribblings/reference/contracts.scrbl > +++ NEW/pkgs/racket-pkgs/racket-doc/scribblings/reference/contracts.scrbl > @@ -6,7 +6,7 @@ > @(define contract-eval > (lambda () > (let ([the-eval (make-base-eval)]) > - (the-eval '(require racket/contract racket/contract/parametric)) > + (the-eval '(require racket/contract racket/contract/parametric > racket/list)) > the-eval))) > > @title[#:tag "contracts" #:style 'toc]{Contracts} > @@ -1430,6 +1430,7 @@ inside the @racket[body] will be protected with > contracts that > blame the context of the @racket[with-contract] form for the positive > positions and the @racket[with-contract] form for the negative ones.} > > +@(define furlongs->feet-eval (contract-eval)) > @defform*[[(define/contract id contract-expr free-var-list init-value-expr) > (define/contract (head args) contract-expr free-var-list body ...+)]]{ > Works like @racket[define], except that the contract > @@ -1437,7 +1438,7 @@ Works like @racket[define], except that the contract > definition of @racket[head] and @racket[args], see @racket[define]. > For the definition of @racket[free-var-list], see @racket[with-contract]. > > -@examples[#:eval (contract-eval) > +@examples[#:eval furlongs->feet-eval > (define/contract distance (>=/c 0) 43.52) > (define/contract (furlongs->feet fr) > (-> real? real?) > @@ -1508,6 +1509,39 @@ The @racket[define-struct/contract] form only allows a > subset of the > (make-salmon #f 'pacific) > ]} > > +@defform[(invariant-contract contract-expr expr)]{ > + Establishes an invariant of @racket[expr], determined by > @racket[contract-expr]. > + > + Unlike other ways to attach contracts to values, an > + @racket[invariant-contract] does not establish a boundary > + between two parties. Instead, it simply puts the contract > + on the value, treating the module containing the > + @racket[invariant-contract] expression as the party to be blamed > + for any violations of the contract. > + > + This means, for example, that the contract is checked on > + recursive calls, when an invariant is used on the right-hand > + side of a definition. > + > + @examples[#:eval > + furlongs->feet-eval > + (define furlongss->feets > + (invariant-contract > + (-> (listof real?) (listof real?)) > + (λ (l) > + (cond > + [(empty? l) empty] > + [else > + (if (= 327 (car l)) > + (furlongss->feets (list "wha?")) > + (cons (furlongs->feet (first l)) > + (furlongss->feets (rest l))))])))) > + > + (furlongss->feets (list 1 2 3)) > + > + (furlongss->feets (list 1 327 3))] > +} > + > @defidform[current-contract-region]{ > Bound by @racket[define-syntax-parameter], this contains > information about the current contract region, used by > > racket/collects/racket/contract/private/base.rkt > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > --- OLD/racket/collects/racket/contract/private/base.rkt > +++ NEW/racket/collects/racket/contract/private/base.rkt > @@ -2,9 +2,10 @@ > > (provide contract > (rename-out [-recursive-contract recursive-contract]) > - current-contract-region) > + current-contract-region > + invariant-contract) > > -(require (for-syntax racket/base syntax/name) > +(require (for-syntax racket/base syntax/name syntax/srcloc) > racket/stxparam > syntax/srcloc > syntax/location > @@ -88,6 +89,16 @@ > (procedure-rename new-val vs-name)])] > [else new-val]))) > > +(define-syntax (invariant-contract stx) > + (syntax-case stx () > + [(_ ctc e) > + (quasisyntax/loc stx > + (let ([me (quote-module-name)]) > + (contract ctc e > + me me > + '#,(syntax-local-infer-name stx) > + '#,(build-source-location-vector #'ctc))))])) > + > (define-syntax (-recursive-contract stx) > (define (do-recursive-contract arg type name) > (define local-name (syntax-local-infer-name stx)) > > racket/collects/racket/contract/region.rkt > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > --- OLD/racket/collects/racket/contract/region.rkt > +++ NEW/racket/collects/racket/contract/region.rkt > @@ -3,7 +3,8 @@ > (provide define-struct/contract > define/contract > with-contract > - current-contract-region) > + current-contract-region > + invariant-contract) > > (require (for-syntax racket/base > racket/struct-info _________________________ Racket Developers list: http://lists.racket-lang.org/dev
