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jregex

Huang Jiahua

The jregex library provides four ways to handle problems with regular expression including matching and searching. And the users are provided with four function.

Matching

The first function provided is to return wheter a string matches the given regular expression.

#include "jregex/jregex.h"
#include <string>
#include <iostream>

const std::string seq = "AGGGCT";
jregex::jreg pat("AG*C?T{1,}");
if (jregex::jregex_match(seq, pat))
    std::cout << "Positive!" << std::endl;

Searching

The second function provided is to return wheter there is a sub-string that matches the given regular expression.

#include "jregex/jregex.h"
#include <string>
#include <iostream>

const std::string seq = "GTCCAGGGCTACTG";
jregex::jreg pat("AG*C?T{1,}");
if (jregex::jregex_search(seq, pat))
    std::cout << "Positive!" << std::endl;

Finding the First

The third function provided is to return the position and length of the sub-string that matches the regular expression. The returned value is a class named jregex::result. It has three member function: position(), length() and str() returning the matching position, the length of the matching sub-string and the sub-string respectively. The str() returns a copy of the sub-string.

#include "jregex/jregex.h"
#include <string>
#include <iostream>

const std::string seq = "GTCCAGGGCTACTG";
jregex::jreg pat("AG*C?T{1,}");
jregex::result re =
	jregex::jreg_find(seq, pat);
if (re.position() != seq.size()) // suggesting matching sucessfully
	std::cout << "It suggests positive from No."
	          << seq.position()
	          << " with " << seq.length()
	          << "characters: " << seq.str()
	          << std::endl;

Finding All

The final function provided return an array of results mentioned above, and the array is stored in a std::vector<result> or jregex::results. Mind that it doesn't matches recursively, for example, the matching position of "AAAA" by the jreg("AA") is 0 and 2, not 0, 1 and 2.

const std::string seq = "GTCACCTTCCA";
jregex::jreg pat("[^AG]CA");
jregex::results arr; // empty
jregex::jregex_find(seq,
                    arr, // reference of the array
                    pat);
for (jregex::result re : arr)
    std::cout << re.str() << std::endl;

Supported Regular Expression Grammer

name notation example
concatenation characters abcd
parentheses enclosed in ( ) a(bc)d
or separated by | (ab|c)d
closure * (ab)*c*
at least 1 + (ab)+c+
0 or 1 ? (ab)?c?
specific times count in { } m{2}d
range of times range in { } m{1,2}d{3,}
wildcard . .+\.cpp
specified set enclosed in [ ] [AEIOU]*
set with range [ ] with - [A-Z][0-9]
complement [ ] with ^ [^AEIOU]*
escape \ \* \+
space \s \S \t \s \S \t ...
digit \d \D \d \D
alpha and digit \w \W \w \W

Not Yet Supported

  • Anchors: ^ and $
  • \b \B representing the boundaries
  • \1 \2 <foo> referencing the clusters
  • ?= ?<= ?! ?<!
  • <.+?>
  • Whatever not mentioned above