Copyright (C) 2002 The University of Melbourne


THE REGEX MODULE

The regex/1 function converts conventional string-type regular expression
definitions into values of type regex.  These regex values can be used
for string matching and search-and-replace operations.

EXAMPLE OF REGEXES

regex(".")		matches any char except `\n'
regex("abc")		matches `abc'
regex("abc*")		matches zero or more contiguous occurrences of `abc'
regex("abc+")		matches one or more contiguous occurrences of `abc'
regex("abc?")		matches zero or one occurrence of `abc'
regex("abc|xyz")	matches `abc' or `xyz'
regex("(abc|xyz)?")	matches zero or one occurrence of `abc' or `xyz'
regex("abc|xyz?")	matches `abc' or zero or one occurrence of `xyz'
regex("[pqr]")		matches `p', `q' or `r'
regex("[p-z]")		matches `p', 'q', ..., or `z'
regex("[abcp-r]")	matches `a', `b', `c', 'p', 'q', ..., or `z'
regex("[]]")		matches `]'
regex("[^...]")		matches any char not in the set ... or `\n'
regex("\\?")		matches `?' (ditto for any other literal char)

There is a corresponding function regexp/1 (note the different spelling)
which converts standard string-type regular expression definitions into
values of type regexp, suitable for use with the lex module.

EXAMPLES OF USE

The following predicates and functions all take values of type regex as
their first argument:

left_match(regex("a+"), "faat cat", Substring, Start, Count)
	fails.

left_match(regex("a+"), "a faat cat", Substring, Start, Count)
	succeeds with Substring = "a", Start = 0, Count = 1.

first_match(regex("a+"), "faat cat", Substring, Start, Count)
	succeeds with Substring = "aa", Start = 1, Count = 2.

right_match(regex("a+"), "faat cat", Substring, Start, Count)
	fails.

right_match(regex("a+"), "kowabunga", Substring, Start, Count)
	succeeds with Substring = "a", Start = 8, Count = 1.

exact_match(regex("a+"), "kowabunga", Substring, Start, Count)
	fails.

exact_match(regex("a+"), "aaaa")
	succeeds.

matches(regex("a+"), "faat cat") = [{"aa", 1, 2}, {"a", 6, 1}]

replace_first(regex("a+"), "f", "faat cat") = "fft cat"

replace_first(regex("a+"), "f", "xyz") = "xyz"

replace_all(regex("a+"), "f", "faat cat") = "fft cft"

replace_all(regex("a+"), "f", "xyz") = "xyz"

change_first(regex("a+"), string__to_upper, "faat cat") = "fAAt cat"

change_first(regex("a+"), string__to_upper, "xyz") = "xyz"

change_all(regex("a+"), string__to_upper, "faat cat") = "fAAt cAt"

change_all(regex("a+"), string__to_upper, "xyz") = "xyz"

