suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

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

Browse Source
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
pkgs/racket-doc/scribblings/reference/contracts.scrbl
View File

@ -1437,7 +1437,15 @@ arguments:
@racketblock[(->i () @racketblock[(->i ()
(#:x [x number?] (#:x [x number?]
#:y [y (x) (>=/c x)]) #: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 The contract expressions are not always evaluated in
order. First, if there is no dependency for a given contract expression, 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 argument), then the contract that appears earlier in the source text is
evaluated first. evaluated first.
If all of the identifier positions of the range If all of the identifier positions of a range contract with
contract are @racket[_]s (underscores), then the range contract expressions a dependency are @racket[_]s (underscores), then the range
are evaluated when the function is called instead of when it returns. contract expressions are evaluated when the function is
Otherwise, dependent range expressions are evaluated when the function called instead of when it returns. Otherwise, dependent
returns. range expressions are evaluated when the function returns.
If there are optional arguments that are not supplied, then If there are optional arguments that are not supplied, then
the corresponding variables will be bound to a special value the corresponding variables will be bound to a special value