[beautiful code] A Regular Expression Matcher : Brian Kernighan & Rob Pike

	// http://genius.cat-v.org/brian-kernighan/articles/beautiful
	// c matches any literal character c
	// . matches any single character
	// ^ matches the beginning of the input string
	// $ matches the end of the input string
	// * matches zero or more occurrences of the previous character
	/* match: search for regexp anywhere in text */
	int match(char *regexp, char *text)
	{
	if (regexp[0] == '^')
	return matchhere(regexp+1, text);
	do { /* must look even if string is empty */
	if (matchhere(regexp, text))
	return 1;
	} while (*text++ != '\0');
	return 0;
	}
	/* matchhere: search for regexp at beginning of text */
	int matchhere(char *regexp, char *text)
	{
	if (regexp[0] == '\0')
	return 1;
	if (regexp[1] == '*')
	return matchstar(regexp[0], regexp+2, text);
	if (regexp[0] == '$' && regexp[1] == '\0')
	return *text == '\0';
	if (*text!='\0' && (regexp[0]=='.' || regexp[0]==*text))
	return matchhere(regexp+1, text+1);
	return 0;
	}
	/* matchstar: search for c*regexp at beginning of text */
	int matchstar(int c, char *regexp, char *text)
	{
	do { /* a * matches zero or more instances */
	if (matchhere(regexp, text))
	return 1;
	} while (*text != '\0' && (*text++ == c || c == '.'));
	return 0;
	}

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