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docs: correct description of custom-port special results

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There no longer seems to be any path that uses the 0-arity option for
a read result from a custom input-port that is a function for a
"special" result. Probably, that path got lost when I added a `source`
optional argument to `read-char-or-special`. If so, that effect of the
change wasn't intentional, but let's just be happy that a
simplification is in place.
This commit is contained in:
Matthew Flatt 2018-10-10 17:45:04 -06:00
parent 16347b434d
commit 694fe2e55c
1 changed files with 5 additions and 22 deletions
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27
pkgs/racket-doc/scribblings/reference/custom-ports.scrbl
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@ -71,8 +71,8 @@ The arguments implement the port as follows:
@item{@racket[eof];} @item{@racket[eof];}
@item{a procedure of arity four (representing a ``special'' @item{a procedure of arity four (representing a ``special''
result, as discussed @elemref["special"]{further below}) and result, as discussed @elemref["special"]{further below}),
optionally of arity zero, but a procedure result is allowed only but a procedure result is allowed only
when @racket[peek] is not @racket[#f];} when @racket[peek] is not @racket[#f];}
@item{a @techlink{pipe} input port that supplies bytes to be @item{a @techlink{pipe} input port that supplies bytes to be
@ -377,26 +377,9 @@ The arguments implement the port as follows:
return a character or @racket[eof]; in particular, @racket[read-char] return a character or @racket[eof]; in particular, @racket[read-char]
raises an exception if it encounters a special-result procedure, even raises an exception if it encounters a special-result procedure, even
if the procedure produces a byte.) A special-result procedure must if the procedure produces a byte.) A special-result procedure must
accept four arguments, and it can optionally accept zero arguments: accept four arguments that represent a source location. The first
argument is @racket[#f] when the special read is triggered by @racket[read]
@itemize[ or @racket[read/recursive].
@item{When the special read is triggered by @racket[read-syntax],
@racket[read-syntax/recursive] the
procedure is passed four arguments that represent a source
location. Four arguments for a source location are also provided when
the read is triggered by @racket[read-byte-or-special],
@racket[read-char-or-special], @racket[peek-byte-or-special], or
@racket[peek-char-or-special] with a non-@racket[#f] source name.}
@item{When the special read is triggered by @racket[read],
@racket[read/recursive], or other calls to
@racket[read-byte-or-special], @racket[read-char-or-special],
@racket[peek-byte-or-special], or @racket[peek-char-or-special], the
procedure is passed no arguments if it accepts zero arguments,
otherwise it is passed four arguments that are all @racket[#f].}
]
The special-value procedure can return an arbitrary value, and it The special-value procedure can return an arbitrary value, and it
will be called zero or one times (not necessarily before further will be called zero or one times (not necessarily before further