How can this pattern be simplified?
/[0-9]+[ \t\r\n\f][a-zA-Z0-9_]*/
We can use metacharacters to replace and simplify our character classes:
Metacharacters are built-in character classes. The \d metacharacter is the
same as the [0-9] character class, \s is the same as [ \t\r\n\f], and
\w is the same as [a-zA-Z0-9_]. With these in mind, we can rewrite our
original pattern much more concisely as:
/\d+\s\w*/
The full list of metacharacters as listed in the [character classes section of the regex class docs][] is:
| Metacharacter | Interpretation |
|---|---|
. |
Any character except a newline |
\w |
A word character ([a-zA-Z0-9_]) |
\W |
A non-word character ([^a-zA-Z0-9_]) |
\d |
A digit character ([0-9]) |
\D |
A non-digit character ([^0-9]) |
\h |
A hex digit character ([0-9a-fA-F]) |
\H |
A non-hex digit character ([^0-9a-fA-F]) |
\s |
A whitespace character: ([ \t\r\n\f]) |
\S |
A non-whitespace character: ([^ \t\r\n\f]) |
[character classes section of the regex class docs]: http://ruby-doc.org/core-2.2.2/Regexp.html#class-Regexp-label-Character+Classes
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