More intuitive escape sequences for string patterns

compiler.c

@@ -395,6 +395,12 @@ vm_op_t *bpeg_stringpattern(file_t *f, const char *str)
         for (; *str; str++) {
             if (*str == '\\') {
                 check(str[1], "Expected more string contents after backslash");
+                const char *after_escape;
+                char e = unescapechar(&str[1], &after_escape);
+                if (e != str[1]) {
+                    str = after_escape - 1;
+                    continue;
+                }
                 if (str[1] == '\\') {
                     ++str;
                     continue;

grammars/bpeg.bpeg

@@ -7,7 +7,7 @@ Def: @[name]id _ `: __ (
     / @[!]{...>(`;/id_`:/$) => "Invalid definition: @0"})
 
 # This is used for command line arguments:
-String-pattern: 0+(`\ pat 0-1`; / .)
+String-pattern: 0+(`\ (escape-sequence / pat 0-1`;) / .)
 
 pat: suffixed-pat / simple-pat
 simple-pat: Upto-and / Dot / String / Char-range / Char / Escape-range / Escape / No
@@ -37,7 +37,6 @@ escape-sequence: (
        `n/`t/`r/`e/`b/`a/`v
       / 1-3 `0-7
       / `x 2 (`0-9/`a-f/`A-F)
-      / .
     )
 No: `! (_@pat / @[!]{=>"Expected a pattern after the exclamation mark"})
 Nodent: `|

grammars/builtins.bpeg

@@ -49,7 +49,7 @@ utf8-codepoint: (
     / \xf0-xf7 3\x80-xbf
 )
 crlf: \r\n
-cr: \r; r: \r
+cr: \r
 anglebraces: `< 0+(anglebraces / !`>$.) `>
 brackets: `[ 0+(brackets / !`]$.) `]
 braces: `{ 0+(braces / !`}$.) `}
@@ -66,9 +66,9 @@ digit: `0-9
 Abc: `a-z/`A-Z
 ABC: `A-Z
 abc: `a-z
-esc: \e; e: \e
-tab: \t; t: \t
-nl: \n; lf: \n; n: \n
+esc: \e
+tab: \t
+nl: \n; lf: \n
 c-block-comment: '/*' ... '*/'
 c-line-comment: '//' ..$
 c-comment: c-line-comment / c-block-comment