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Pattern Syntax

The reference tables. The reader will come back to scan these.

Character Classes

PatternMatches
.Any character except newline
\dDigit (0–9)
\DNon-digit
\wWord character (letter, digit, underscore)
\WNon-word character
\sWhitespace
\SNon-whitespace
[abc]Any of a, b, c
[^abc]Any character NOT a, b, c
[a-z]Any character in range a–z

Quantifiers

PatternMeaning
*Zero or more
+One or more
?Zero or one
{n}Exactly n
{n,}n or more
{n,m}Between n and m
*?, +?, ??Non-greedy (lazy) versions

Anchors and Boundaries

PatternMeaning
^Start of string (or line with m flag)
$End of string (or line with m flag)
\bWord boundary
\BNon-word boundary

Grouping and Alternation

PatternMeaning
a|ba or b
(...)Capture group
(?:...)Non-capturing group
(?<name>...)Named capture group

Complete Examples

;; Match a date: YYYY-MM-DD
(bind date-pattern (regex "^(\\d{4})-(\\d{2})-(\\d{2})$"))

;; Match an email (simple)
(bind email-pattern (regex "^\\S+@\\S+\\.\\S+$"))

;; Match a hex color
(bind hex-color (regex "^#([0-9a-fA-F]{3}|[0-9a-fA-F]{6})$"))