Add R7RS character names as extensions

LOG

@@ -2336,3 +2336,7 @@
     c/foreign.c
 - Propagate immutable versions of "", #(), #vu8() and #vfx() in cp0.
     s/cp0.ss s/cpnanopass.ss
+- add #\null and #\escape as aliases for #\nul and #\esc (R7RS compatibility)
+    mats/6.ms s/read.ss
+- allow \| escape inside strings (R7RS compatibility)
+    mats/6.ms s/read.ss

csug/objects.stex

@@ -339,6 +339,8 @@ Second, it recognizes several nonstandard named characters:
 \scheme{#\rubout} (which is the same as \scheme{#\delete}),
 \scheme{#\bel} (which is the same as \scheme{#\alarm}),
 \scheme{#\vt} (which is the same as \scheme{#\vtab}),
+\scheme{#\escape} (which is the same as \scheme{#\esc}),
+\scheme{#\null} (which is the same as \scheme{#\nul}),
 \scheme{#\nel} (the Unicode NEL character), and
 \scheme{#\ls} (the Unicode LS character).
 The set of nonstandard character names may be changed via the procedure
@@ -418,8 +420,9 @@ ASCII code for the character.
 
 \section{Strings}
 
-{\ChezScheme} extends the standard string syntax with two character
-escapes: \scheme{\'}, which produces the single quote character, and
+{\ChezScheme} extends the standard string syntax with three character
+escapes: \scheme{\'}, which produces the single quote character,
+\scheme{\|}, which produces the vertical bar character, and
 \scheme{\\var{nnn}}, i.e., backslash followed by 3 octal digits,
 which produces the character equivalent of the octal value of
 the 3 digits.

mats/6.ms

@@ -1558,6 +1558,9 @@
   (eqv? (char-name 'rubout) #\rubout)
   (eqv? (char-name #\nul) 'nul)
   (eqv? (char-name 'nul) #\nul)
+  (eqv? (char-name #\null) 'nul)
+  (eqv? (char-name 'null) #\nul)
+  (eqv? #\nul #\null)
   (eqv? (char-name 'foo) #f)
   (eqv? (char-name 'delete) #\delete)
   (eqv? (char-name #\delete) 'delete)
@@ -1567,6 +1570,9 @@
   (eqv? (char-name #\alarm) 'alarm)
   (eqv? (char-name 'esc) #\esc)
   (eqv? (char-name #\esc) 'esc)
+  (eqv? (char-name 'escape) #\esc)
+  (eqv? (char-name #\escape) 'esc)
+  (eqv? #\esc #\escape)
   (error? (read (open-input-string "#\\foo")))
   (and (eqv? (char-name 'foo #\003) (void))
        (eqv? (char-name 'foo) #\003)
@@ -1595,6 +1601,7 @@
   (eqv? (string-ref "\\\"\'" 0) #\\)
   (eqv? (string-ref "\\\"\'" 1) #\")
   (eqv? (string-ref "\\\"\'" 2) #\')
+  (eqv? (string-ref "\|\v" 0) #\|)
   (= (char->integer (string-ref "a\012" 1)) #o12 10)
   (= (char->integer (string-ref "a\015" 1)) #o15 13)
   (= (char->integer (string-ref "a\177" 1)) #o177 127)

release_notes/release_notes.stex

@@ -58,6 +58,13 @@ Online versions of both books can be found at
 %-----------------------------------------------------------------------------
 \section{Functionality Changes}\label{section:functionality}
 
+\subsection{R7RS compatibility extensions (9.6.0)}
+
+The reader now accepts \scheme{#\null} and \scheme{#\escape} as alternative
+spellings of the characters \scheme{#\nul} and \scheme{#\esc}, respectively.
+
+The reader now accepts \scheme{\|} inside strings.
+
 \subsection{Unicode 14.0 Support (9.6.0)}
 
 The character sets, character classes, and word-breaking algorithms for character, string,

s/read.ss

@@ -854,6 +854,10 @@
               (nonstandard "\\' string character")
               (with-stretch-buffer i c
                 (*state rd-token-string (fx+ i 1)))]
+             [(#\|)
+              (nonstandard "\\| string character")
+              (with-stretch-buffer i c
+                (*state rd-token-string (fx+ i 1)))]
              [else (let ([bfp char-bfp])
                      (xcall rd-error #f #t "invalid string character \\~c" c))]))]
         [(#\newline #\nel #\ls)
@@ -1892,9 +1896,11 @@
   (char-name 'newline #\newline) ; must come after linefeed entry
   (char-name 'backspace #\backspace)
   (char-name 'rubout #\rubout)
+  (char-name 'null #\nul)
   (char-name 'nul #\nul)
   (char-name 'bel #\bel)
   (char-name 'vt #\vt)
+  (char-name 'escape #\esc)
   (char-name 'esc #\esc)
   (char-name 'vtab #\vtab)
   (char-name 'delete #\rubout)