# Regex

Regex is based on PCRE (Perl Compatible Regular Expressions) and built on top of Erlang's `:re` module. More information can be found in the [`:re` module documentation](http://www.erlang.org/doc/man/re.html).

```elixir
# A simple regular expression that matches foo anywhere in the string
~r/foo/

# A regular expression with case insensitive and Unicode options
~r/foo/iu

#Internally a struct so matches
~r/(?<foo>.)(?<bar>.)/ == ~r/(?<foo>.)(?<bar>.)/


~r/https?.*example\d?\.com$/
~r/https?.*eta-pr-[[:digit:]]+.onrender.com$/ #matches "https://eta-pr-455.onrender.com" where number can change
```

## Usage

```elixir
String.match?("123", ~r/^[[:alnum:]]+$/) #true
String.match?("123 456", ~r/^[[:alnum:][:blank:]]+$/) #true
```

The supported class names are:

* alnum - Letters and digits
* alpha - Letters
* ascii - Character codes 0-127
* blank - Space or tab only
* cntrl - Control characters
* digit - Decimal digits (same as \d)
* graph - Printing characters, excluding space
* lower - Lowercase letters
* print - Printing characters, including space
* punct - Printing characters, excluding letters, digits, and space
* space - Whitespace (the same as \s from PCRE 8.34)
* upper - Uppercase letters
* word - "Word" characters (same as \w)
* xdigit - Hexadecimal digits


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