<INTERFACE> The <CD/REGEXP_PARSER/ signature <SEEALSO> <STRREF/RegExpSyntax/ </SEEALSO> <PP> This is the signature of a concrete syntax for regular expressions. It provides functionality to converts strings of characters into the abstract syntax of regular expressions given in the <CD/RegExpSyntax/ structure. This is done by converting a character reader into an abstract syntax reader.<PP> The <CD/AwkSyntax/ structure is a structure matching this signature. It implements the AWK syntax for specifying regular expressions. The syntax is defined on pp. 28-30 of "The AWK Programming Language," by Aho, Kernighan and Weinberger.<PP> `Meta characters: "\" "^" "$" "." "[" "]" "|" "(" ")" "*" "+" "?" Atomic REs: c matches the character c (for non-metacharacters c) "^" matches the empty string at the beginning of a line "$" 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. Compound regular expressions: 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")" matches A` <PP> <SPEC> <VAL>scan<TY>(char,'a) StringCvt.reader -> (RegExpSyntax.syntax,'a) StringCvt.reader <COMMENT> <PROTOTY> scan <ARG/getc/ </PROTOTY> Given a character reader <ARG/getc/, this function returns a reader that parses elements of the stream into the abstract syntax for regular expressions. <SIGINSTANCE><ID>AwkSyntax </INTERFACE>