The `AwkSyntax` structure

The `AwkSyntax` structure implements the AWK syntax for regular expressions. The syntax is defined on pp. 28-30 of The AWK Programming Language, by Aho, Kernighan and Weinberger. The syntax has been extended with interval syntax, which was added as part of the POSIX standard.

Synopsis

``structure AwkSyntax : REGEXP_PARSER``

Description

The meta characters are: "\" "^" "$" "." "[" "]" "|" "(" ")" "*" "+" "?" ```Atomic REs: c matches the character c (for non-metacharacters c) "^" matches the empty string at the beginning of a line "$"	matches the empty string at the end of a line
"."	matches any single character (except \000 and \n)```
```Escape sequences:
"\b"	matches backspace
"\f"	matches formfeed
"\n"	matches newline (linefeed)
"\r"	matches carriage return
"\t"	matches tab
"\"ddd	matches the character with octal code ddd.
"\"c	matches the character c (e.g., \\ for \, \" for ")
"\x"dd  matches the character with hex code dd.```
```Character classes:
[...]	matches any character in "..."
[^...]	a complemented character list, which matches any character not
in the list "..."```
```Compound regular expressions, where A and B are REs:
A|B	matches A or B
AB	matches A followed by B
A?	matches zero or one As
A*	matches zero or more As
A+	matches one or more As
A{n}	matches n copies of A
A{n,}	matches n copies of A
A{n,m}	matches n copies of A
(A)	matches A```