Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

r"
"
g

Test String

Code Generator

Generated Code

re = /(?<=\[)(?!:scroll:)(?!\d+)(?P<title>[A-Z][\w\s\,\-\?\:\']+)(?=\])/ str = '# Functional Programming * [:scroll:](organizing-programs-without-classes.pdf) [Organizing Programs Without Classes](http://cs.au.dk/~hosc/local/LaSC-4-3-pp223-242.pdf) * [:scroll:](functional-programming-with-bananas-lenses-envelops-and-barbed-wire.pdf) [Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire](http://eprints.eemcs.utwente.nl/7281/01/db-utwente-40501F46.pdf) From Patrick Thomson\'s [An introduction to Recursion Schemes](http://patrickthomson.ghost.io/an-introduction-to-recursion-schemes/): > In 1991, Erik Meijer, Maarten Fokkinga, and Ross Paterson published their now-classic paper Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire. Though this paper isn’t widely known outside of the functional programming community, its contributions are astonishing: the authors use category theory to express a set of simple, composable combinators, called recursion schemes, that automate the process of traversing and recursing through nested data structures. Though recursion schemes predate Meijer et. al’s work, this paper brings the enormous abstractive power of category theory to bear on the subject of traversing data structures—it’s a magnificent example of how category-theoretical concepts can bring both rigor and simplicity to day-to-day programming tasks. * :scroll: [Equal Rights for Functional Objects or, The More Things Change, The More They Are the Same](equal-rights-for-functional-objects.pdf) * :scroll: [Optimal Purely Functional Priority Queues](optimal-purely-functional-priority-queues.pdf) * :scroll: [Why Functional Programming Matters](why-functional-programming-matters.pdf) ## Applicative Programming * [Backtracking Iterators](https://www.lri.fr/~filliatr/publis/enum2.pdf) * [Breadth-First Numbering: Lessons from a Small Exercise in Algorithm Design](http://www.cs.tufts.edu/~nr/cs257/archive/chris-okasaki/breadth-first.pdf) ## Concatenative Programming * :scroll: [Concatenative Programming: An Overlooked Paradigm in Functional Programming](concatenative-programming-an-overlooked-paradigm.pdf) ## Imperative Programming - Functional Programming * [Crossing the Gap from Imperative to Functional Programming through Refactoring](http://dig.cs.illinois.edu/papers/lambdaRefactoring.pdf)' # Print the match result str.scan(re) do |match| puts match.to_s end

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html