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

add some reader forms to the index

Browse Source 
svn: r7769
This commit is contained in:
Matthew Flatt 2007-11-19 22:17:07 +00:00
parent 24980e41ce
commit c04cf36c29
1 changed files with 51 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

99
collects/scribblings/reference/reader.scrbl
View File

@ -508,20 +508,21 @@ A @as-index{@litchar{;}} starts a line comment. When the reader
encounters @litchar{;}, then it skips past all characters until the
next linefeed or carriage return.
A @litchar["#|"] starts a nestable block comment. When the reader
encounters @litchar["#|"], then it skips past all characters until a
closing @litchar["|#"]. Pairs of matching @litchar["#|"] and
A @as-index{@litchar["#|"]} starts a nestable block comment. When the
reader encounters @litchar["#|"], then it skips past all characters
until a closing @litchar["|#"]. Pairs of matching @litchar["#|"] and
@litchar["|#"] can be nested.
A @litchar{#;} starts an S-expression comment. Then the reader
encounters @litchar{#;}, it recursively reads one datum, and then
discards the datum (continuing on to the next datum for the read
A @as-index{@litchar{#;}} starts an S-expression comment. Then the
reader encounters @litchar{#;}, it recursively reads one datum, and
then discards the datum (continuing on to the next datum for the read
result).
A @litchar{#! } (which is @litchar{#!} followed by a space) or
@litchar{#!/} starts a line comment that can be continued to the next
line by ending a line with @litchar["\\"]. This form of comment
normally appears at the beginning of a Unix script file.
A @as-index{@litchar{#! }} (which is @litchar{#!} followed by a space)
or @as-index{@litchar{#!/}} starts a line comment that can be
continued to the next line by ending a line with @litchar["\\"]. This
form of comment normally appears at the beginning of a Unix script
file.
@reader-examples[
"; comment"
@ -563,18 +564,18 @@ vector's elements are also wraped as syntax objects.
@section[#:tag "parse-hashtable"]{Reading Hash Tables}
A @litchar{#hash} starts an immutable hash-table constant with key
matching based on @scheme[equal?]. The characters after @litchar{hash}
must parse as a list of pairs (see @secref["parse-pair"]) with a
specific use of delimited @litchar{.}: it must appear between the
elements of each pair in the list, and nowhere in the sequence of list
elements. The first element of each pair is used as the key for a
table entry, and the second element of each pair is the associated
value.
A @as-index{@litchar{#hash}} starts an immutable hash-table constant
with key matching based on @scheme[equal?]. The characters after
@litchar{hash} must parse as a list of pairs (see
@secref["parse-pair"]) with a specific use of delimited @litchar{.}:
it must appear between the elements of each pair in the list, and
nowhere in the sequence of list elements. The first element of each
pair is used as the key for a table entry, and the second element of
each pair is the associated value.
A @litchar{#hasheq} starts a hash table like @litchar{#hash}, except
that it constructs a hash table based on @scheme[eq?] instead of
@scheme[equal?].
A @as-index{@litchar{#hasheq}} starts a hash table like
@litchar{#hash}, except that it constructs a hash table based on
@scheme[eq?] instead of @scheme[equal?].
In either case, the table is constructed by adding each mapping to the
hash table from left to right, so later mappings can hide earlier
@ -591,9 +592,10 @@ In either case, the table is constructed by adding each mapping to the
@section[#:tag "parse-box"]{Reading Boxes}
When the reader encounters a @litchar{#&}, it starts parsing a box;
see @secref["boxes"] for information on boxes. The content of the box
is determined by recursively reading the next datum.
When the reader encounters a @as-index{@litchar{#&}}, it starts
parsing a box; see @secref["boxes"] for information on boxes. The
content of the box is determined by recursively reading the next
datum.
In @scheme[read-syntax] mode, the recursive read for the box content
is also in @scheme[read-syntax] mode, so that the wrapped box's
@ -607,8 +609,8 @@ content is also wraped as a syntax object.
@guideintro["characters"]{the syntax of characters}
A @litchar["#\\"] starts a character constant, which has one of the
following forms:
A @as-index{@litchar["#\\"]} starts a character constant, which has
one of the following forms:
@itemize{
@ -655,10 +657,10 @@ following forms:
@section[#:tag "parse-keyword"]{Reading Keywords}
A @litchar{#:} starts a keyword. The parsing of a keyword after the
@litchar{#:} is the same as for a symbol, including case-folding in
case-insensitive mode, except that the part after @litchar{#:} is
never parsed as a number.
A @as-index{@litchar{#:}} starts a keyword. The parsing of a keyword
after the @litchar{#:} is the same as for a symbol, including
case-folding in case-insensitive mode, except that the part after
@litchar{#:} is never parsed as a number.
@reader-examples[
"#:Apple"
@ -667,14 +669,14 @@ never parsed as a number.
@section[#:tag "parse-regexp"]{Reading Regular Expressions}
A @litchar{#rx} or @litchar{#px} starts a regular expression. The
characters immediately after @litchar{#rx} or @litchar{#px} must parse
as a string or byte string (see @secref["parse-string"]). A
@litchar{#rx} prefix starts a regular expression as would be
constructed by @scheme[regexp], @litchar{#px} as
constructed by @scheme[pregexp], @litchar{#rx#} as
constructed by @scheme[byte-regexp], and @litchar{#px#} as
constructed by @scheme[byte-pregexp].
A @as-index{@litchar{#rx}} or @as-index{@litchar{#px}} starts a
regular expression. The characters immediately after @litchar{#rx} or
@litchar{#px} must parse as a string or byte string (see
@secref["parse-string"]). A @litchar{#rx} prefix starts a regular
expression as would be constructed by @scheme[regexp], @litchar{#px}
as constructed by @scheme[pregexp], @litchar{#rx#} as constructed by
@scheme[byte-regexp], and @litchar{#px#} as constructed by
@scheme[byte-pregexp].
@reader-examples[
"#rx\".*\""
@ -715,8 +717,9 @@ neither defines nor uses graph tags for other top-level forms.
@section[#:tag "parse-reader"]{Reading via an External Reader}
When the reader encounters @litchar{#reader}, then it loads an
external reader procedure and applies it to the current input stream.
When the reader encounters @as-index{@litchar{#reader}}, then it loads
an external reader procedure and applies it to the current input
stream.
The reader recursively reads the next datum after @litchar{#reader},
and passes it to the procedure that is the value of the
@ -740,14 +743,14 @@ If the @scheme[read-accept-reader] @tech{parameter} is set to
@scheme[#f], then if the reader encounters @litchar{#reader}, the
@exnraise[exn:fail:read].
The @litchar{#lang} reader form is similar, but more constrained: the
@litchar{#lang} must be followed by a single space (ASCII 32), and
then a non-empty sequence of alphanumeric ASCII, @litchar{+},
@litchar{-}, @litchar{_}, and/or @litchar{/} characters terminated by
@schemelink[char-whitespace?]{whitespace} or an end-of-file. The
sequence must not start or end with @litchar{/}. A sequence
@litchar{#lang }@nonterm{name} is equivalent to
@litchar{#reader (lib "}@nonterm{name}@litchar{/lang/reader.ss")}.
The @as-index{@litchar{#lang}} reader form is similar, but more
constrained: the @litchar{#lang} must be followed by a single space
(ASCII 32), and then a non-empty sequence of alphanumeric ASCII,
@litchar{+}, @litchar{-}, @litchar{_}, and/or @litchar{/} characters
terminated by @schemelink[char-whitespace?]{whitespace} or an
end-of-file. The sequence must not start or end with @litchar{/}. A
sequence @litchar{#lang }@nonterm{name} is equivalent to
@litchar{#reader }@nonterm{name}@litchar{/lang/reader)}.
By convention, @litchar{#lang} normally appears at the beginning of a
file, possibly after comment forms, to specify the syntax of a module.