From 0d2908f824ab573e9ad13f14919ae4d07984dc89 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 22 Jun 2017 12:22:16 -0600
Subject: [PATCH] regexp docs: minor corrections

Fixes inaccuracies discovered when reimplementing
regexp matching in Racket.
---
 pkgs/racket-doc/scribblings/reference/regexps.scrbl |  4 ++++
 pkgs/racket-doc/scribblings/reference/rx.rkt        | 10 ++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/pkgs/racket-doc/scribblings/reference/regexps.scrbl b/pkgs/racket-doc/scribblings/reference/regexps.scrbl
index 17632df90c..c8d1377fe3 100644
--- a/pkgs/racket-doc/scribblings/reference/regexps.scrbl
+++ b/pkgs/racket-doc/scribblings/reference/regexps.scrbl
@@ -95,6 +95,10 @@ The following completes the grammar for @racket[pregexp], which uses
 
 @px-table
 
+In case-insensitive mode, a backreference of the form
+@litchar{\}@nonterm{n} matches case-insensitively only with respect to
+ASCII characters.
+
 The Unicode categories follow.
 
 @category-table
diff --git a/pkgs/racket-doc/scribblings/reference/rx.rkt b/pkgs/racket-doc/scribblings/reference/rx.rkt
index 6d49304819..455c83be2b 100644
--- a/pkgs/racket-doc/scribblings/reference/rx.rkt
+++ b/pkgs/racket-doc/scribblings/reference/rx.rkt
@@ -9,7 +9,7 @@
 (define grammar @string-append{
   Regexp   ::= Pces               Match Pces                                      #co
             |  Regexp|Regexp      Match either Regexp, try left first             #co 1
-  Pces     ::= Pce                Match Pce                                       #co
+  Pces     ::=                    Match empty                                     #co
             |  PcePces            Match Pce followed by Pces                      #co
   Pce      ::= Repeat             Match Repeat, longest possible                  #co 3
             |  Repeat?            Match Repeat, shortest possible                 #co 6
@@ -22,6 +22,7 @@
             |  Atom{N,}           Match Atom N or more times                      #px 8
             |  Atom{,M}           Match Atom between 0 and M times                #px 9
             |  Atom{N,M}          Match Atom between N and M times                #px 10
+            |  Atom{}             Match Atom 0 or more times                      #px
   Atom     ::= (Regexp)           Match sub-expression Regexp and report          #co 11
             |  [Rng]              Match any character in Rng                      #co 2
             |  [^Rng]             Match any character not in Rng                  #co 12
@@ -34,6 +35,7 @@
             |  Look               Match empty if Look matches                     #co
             |  (?TstPces|Pces)    Match 1st Pces if Tst, else 2nd Pces            #co 36
             |  (?TstPces)         Match Pces if Tst, empty if not Tst             #co
+            |  \`at`end`of`pattern` Match the nul character (ASCII 0)             #co
   Atom     ::= ...                ...                                             #px
             |  \N                 Match latest reported match for N##th _(_       #px 16
             |  Class              Match any character in Class                    #px
@@ -64,7 +66,7 @@
             |  (?!Regexp)         Match if Regexp doesn't match                   #mode 32
             |  (?<=Regexp)        Match if Regexp matches preceding               #mode 33
             |  (?<!Regexp)        Match if Regexp doesn't match preceding         #mode 34
-  Tst      ::= (N)                True if Nth _(_ has a match                     #mode
+  Tst      ::= (N)                True if N##th _(_ has a match                   #mode
             |  Look               True if Look matches                            #mode 36
   Lirng    ::= ...                ...                                             #px
             |  Class              Lirng contains all characters in Class          #px
@@ -170,6 +172,10 @@
     [(#rx"^(.*?)##(.*)$" X Y)
      `(,@(fixup-ids X) ,@(fixup-ids Y))]
     [(#rx"^\\.\\.\\.$") (list (element #f (list s)))]
+    [(#rx"^([^`]*)`(.*)`$" X Y) (append (fixup-ids X)
+                                        (list
+                                         (element #f " ")
+                                         (element #f (regexp-replace* #rx"`" Y " "))))]
     [(#rx"^$") null]
     [else (list s)]))