regex.md

class Regex

Overview

class Regex is for Regular expression.

Supported Regular Expression

Supported all features of Oniguruma. See below for details.

• https://github.com/kkos/oniguruma/blob/master/doc/RE

Regular Expression Literal

You can use a regular expression as literal with surrounded by /. Between / and /, you do not have to escape characters like \n.

/ab+[\t\n]/

The above example is the same as below.

new Regex("ab+[\\t\\n]");  // same as /ab+[\t\n]/
new Regex(%|ab+[\t\n]|);   // same as /ab+[\t\n]/

If you want to change the character of / for a literal, any character used with the prefix of %m is available. In that case, you do not have to escape a character except the character used with the prefix of %m.

If you use a bracket character, you can use a close character corresponding to the open character which you used.

%m<ab+[\t\n]>  // same as /ab+[\t\n]/
%m(ab+[\t\n])  // same as /ab+[\t\n]/

=~ Operator and =~ Operator

These operators are described at the document below. Please see the document below for details.

• Matching Operation

Methods for String

A regular expression object can be directly used for the following methods of a string.

replace

• replace ... Use as specifying a condition string.

var s = "xabbbbbcabbc".replace(/ab+/, ",");
System.println(s);

Here is the result.

x,c,c

split

• split ... Use as a separator condition.

var s = "xabbbbbcabbc".split(/ab+/);
s.each(&(e) => System.println(e));

Here is the result.

x
c
c

Notes

There is a note when it is used in a condition expression of loop like while.

For example, you can loop until not matched with the string of str. But if the loop has ended by such as break, there is a situation that the regular expression object has not correctly been reset in the start of the next loop.

while (group = (str =~ /ab+/)) {
    /* block */
}

A regular expression object will be reset with the following 2 situations.

• The first evaluation. It includes th situation where the last same loop has been completed correctly.
• A content of str has been changed.

This is currently a restriction.

Examples

Example 1. =~ Operator

Code

var a = "111/aaa/bbb/ccc/ddd";
while (group = (a =~ /\w+\//)) {
    for (var i = 0, len = group.length(); i < len; ++i) {
        System.println("found[%2d,%2d) = %s"
            % group[i].begin
            % group[i].end
            % group[i].string);
    }
}

Result

found[ 0, 4) = 111/
found[ 4, 8) = aaa/
found[ 8,12) = bbb/
found[12,16) = ccc/

Example 2. =! Operator

Code

var s = "XYZXYZ";
if (s !~ /ABC/) {
    System.println("ABC is not included.");
}

Result

ABC is not included.

Example 3. String#replace()

Code

var s = "xabbbbbcabbc".replace(/ab+/, ",");
System.println(s);

Result

x,c,c

Example 4. String#split()

Code

var s = "xabbbbbcabbc".split(/ab+/);
s.each(&(e) => System.println(e));

Result

x
c
c

Example 5. %m Prefix (1)

Code

var a = "111/aaa/bbb/ccc/ddd";
while (group = (a =~ %m(\w+/))) {
    for (var i = 0, len = group.length(); i < len; ++i) {
        System.println("found[%2d,%2d) = %s"
            % group[i].begin
            % group[i].end
            % group[i].string);
    }
}

Result

found[ 0, 4) = 111/
found[ 4, 8) = aaa/
found[ 8,12) = bbb/
found[12,16) = ccc/

Example 6. %m Prefix (2)

Code

var a = "111/aaa/bbb/ccc/ddd";
while (group = (a =~ %m<\w+/>)) {
    for (var i = 0, len = group.length(); i < len; ++i) {
        System.println("found[%2d,%2d) = %s"
            % group[i].begin
            % group[i].end
            % group[i].string);
    }
}

Result

found[ 0, 4) = 111/
found[ 4, 8) = aaa/
found[ 8,12) = bbb/
found[12,16) = ccc/

Example 7. %m Prefix (3)

Code

var a = "111/aaa/bbb/ccc/ddd";
while (group = (a =~ %m1\w+/1)) {
    for (var i = 0, len = group.length(); i < len; ++i) {
        System.println("found[%2d,%2d) = %s"
            % group[i].begin
            % group[i].end
            % group[i].string);
    }
}

Result

found[ 0, 4) = 111/
found[ 4, 8) = aaa/
found[ 8,12) = bbb/
found[12,16) = ccc/