Part II: Server Side, JavaScript, and Flash; Oh My!
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Back - references are used to make assumptions on already parsed portions of the test string. In this case,
the pattern defines that the test string must begin with a vowel, be followed by any number and type of
characters, and be concluded with the same vowel encountered at the beginning (case - insensitive
because of the i option).
class Main
{
public static function main()
{
var re = ~/^([aeiou]).*\1$/i;
trace(re.match(???area??™)); // true
trace(re.match(???are??™)); // false
}
}
Alternation has the lowest priority and, thus, can be used in groups. In the following example, a non -
capturing group has been used because there is no interest in retrieving the matched portion defined by
the alternation.
class Main
{
public static function main()
{
var re = ~/j(?:oh|ea)n/i;
trace(re.match(???John??™)); // true
trace(re.match(???Jean??™)); // true
}
}
Look - around, Conditionals, and Comments
Look - around constructs permit you to verify that the pattern is preceded or followed by an expression
without including that expression in the match.
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