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add a mention of the flat/chaperone/impersonator contract hierarchy to the contract docs

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Robby Findler 2012-08-28 13:18:09 -05:00
parent 763882f651
commit fc03ab6c69
2 changed files with 36 additions and 3 deletions
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33
collects/scribblings/reference/contracts.scrbl
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@ -68,6 +68,36 @@ failed, and anything else to indicate it passed.}
]
Contracts in Racket are subdivided into three different categories:
@itemlist[@item{@deftech{Flat contract}s can be fully checked immediately for
a given value. These kinds of contracts are essentially
predicate functions. Using @racket[flat-contract-predicate],
you can extract the predicate from a flat contract, and
@racket[flat-contract?] recognizes a flat contract.}
@item{@deftech{Chaperone contracts} are not always immediately
checkable, but are guaranteed to not change any properties
of any values that they check. That is, they may wrap
a value in such a way that it signals contract violations
later, as the value is used (e.g., a function contract
checks the inputs and outputs to the function only when
the function is called and returned), but any properties
that the value had before being wrapped by the contract
are preserved by the contract wrapper.
All flat contracts are also chaperone contracts (but
not vice-versa).}
@item{@deftech{Impersonator contracts} do not provide any
guarantees about values they check. Impersonator contracts
may hide properties of values, or even make them completely
opaque (e.g, @racket[new-∀/c]).
All contracts are impersonator contracts.}]
For more about this hierarchy, see @tech{chaperones} and
a research paper on chaperones, impersonators, and how they can be used to
implement contracts @cite{Strickland12}.
@local-table-of-contents[]
@; ----------------------------------------
@ -75,9 +105,6 @@ failed, and anything else to indicate it passed.}
@section[#:tag "data-structure-contracts"]{Data-structure Contracts}
@declare-exporting-ctc[racket/contract/base]
A @deftech{flat contract} can be fully checked immediately for
a given value.
@defproc[(flat-contract [predicate (any/c . -> . any/c)]) flat-contract?]{
Constructs a @tech{flat contract} from @racket[predicate]. A value

6
collects/scribblings/reference/reference.scrbl
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@ -182,6 +182,12 @@ The @racketmodname[racket] library combines
#:url "http://srfi.schemers.org/srfi-42/"
#:date "2003")
(bib-entry #:key "Strickland12"
#:title "Chaperones and Impersonators: Run-time Support for Reasonable Interposition"
#:author "T. Stephen Strickland, Sam Tobin-Hochstadt, Matthew Flatt, and Robert Bruce Findler"
#:location "Object-Oriented Programming, Systems, and Languages (OOPSLA"
#:url "http://www.eecs.northwestern.edu/~robby/pubs/papers/oopsla2012-stff.pdf"
#:date "2012")
)
@;------------------------------------------------------------------------