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edit ->i docs along the lines of the discussion in #2822

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This commit is contained in:
Robby Findler 2019-09-15 17:46:57 -05:00
parent 17c424b553
commit f61efeaf80
1 changed files with 14 additions and 6 deletions
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20
pkgs/racket-doc/scribblings/reference/contracts.scrbl
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@ -1437,7 +1437,15 @@ arguments:
@racketblock[(->i ()
(#:x [x number?]
#:y [y (x) (>=/c x)])
[result (x y) (and/c number? (>=/c (+ x y)))])]
[result (x y)
(and/c number?
(if (and (number? x) (number? y))
(>=/c (+ x y))
any/c))])]
The conditional in the range that tests @racket[_x] and @racket[_y]
is necessary to cover the situation where @racket[_x] or @racket[_y]
are not supplied by the calling context (meaning they might be bound
to @racket[the-unsupplied-arg]).
The contract expressions are not always evaluated in
order. First, if there is no dependency for a given contract expression,
@ -1455,11 +1463,11 @@ there is no dependency between two arguments (or the result and an
argument), then the contract that appears earlier in the source text is
evaluated first.
If all of the identifier positions of the range
contract are @racket[_]s (underscores), then the range contract expressions
are evaluated when the function is called instead of when it returns.
Otherwise, dependent range expressions are evaluated when the function
returns.
If all of the identifier positions of a range contract with
a dependency are @racket[_]s (underscores), then the range
contract expressions are evaluated when the function is
called instead of when it returns. Otherwise, dependent
range expressions are evaluated when the function returns.
If there are optional arguments that are not supplied, then
the corresponding variables will be bound to a special value