Regular Expressions 101

Definition Group(?(DEFINE) (?<weeks>mon|tue|wed|thu|fri|sat|sun) )

Group weeks(?<weeks>mon|tue|wed|thu|fri|sat|sun)

1st Alternativemon

monthe literal text mon (case insensitive)

2nd Alternativetue

tuethe literal text tue (case insensitive)

3rd Alternativewed

wedthe literal text wed (case insensitive)

4th Alternativethu

thuthe literal text thu (case insensitive)

5th Alternativefri

frithe literal text fri (case insensitive)

6th Alternativesat

satthe literal text sat (case insensitive)

7th Alternativesun

sunthe literal text sun (case insensitive)

^start of string

Group weekdays(?P<weekdays> (?: \b (?&weeks) (?:\.\.(?&weeks))? ,? )* )

Non-Capturing Group(?: \b (?&weeks) (?:\.\.(?&weeks))? ,? )*

*repeats the group contents below any number of times:

\ban ASCII word boundary

(?&weeks)calls group weeks as a subroutine

Non-Capturing Group(?:\.\.(?&weeks))?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

(?&weeks)calls group weeks as a subroutine

,?optionally matches the literal , (44₁₀ / 54₈ / 2C₁₆)

$end of string, or before its final line terminator

Global pattern flags

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

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Regular Expression

(?(DEFINE)
   (?<weeks>mon|tue|wed|thu|fri|sat|sun)
)
^(?P<weekdays>
    (?:                        
        \b
        (?&weeks)
        (?:\.\.(?&weeks))?
        ,?
    )*
)$

Regular Expression

Unit Tests