Revision ec3bbc17-674c-46d3-b5d2-be458bbcd67c - Code Golf Stack Exchange

# Regex

## Length 1 snippet

 .

`.`, called dot-all, is available in all flavors I had a chance to look at.

### What does it match?

**Java `Pattern`**: In default mode, dot-all matches any code point, except for these 5 code points `\r\n\u0085\u2028\u2029`. With `UNIX_LINES` mode on (but without `DOTALL`), dot-all matches any code point, except for `\n`. With `DOTALL` mode on, dot-all matches any code point. From Java 5, `Pattern` operates on code point, so astral characters are matched by dot-all.

**Python `re`** (tested on 2.7.8 and 3.2.5, may be different on 3.3+): In default mode, dot-all matches any UTF-16 code unit (0000 to FFFF inclusive), except for `\n`. `re.DOTALL` lifts the exception and makes `.` matches any UTF-16 code unit. In these versions, `re` operates on UTF-16 code units, so `.` only manages to match one code unit of characters in astral plane.

**.NET**: Same as Python. The dot-all mode in .NET is called `Singleline`.

**JavaScript (C++11 `<regex>`)**: In default mode, dot-all matches any UTF-16 code unit, except for these 4 code points `\n\r\u2028\u2029`. With `s` flag on, dot-all matches any UTF-16 code unit. JavaScript also operates on UTF-16 code units.

**PCRE**: Depending on build option, dot-all can exclude `\r`, `\n` or `\r\n`, or all 3 CR LF sequences, or any Unicode newline sequence in default mode. In default mode, the engine operates on code unit (can be 8, 16, or 32-bit code unit), so dot-all matches any code unit, except for the newline sequences. In UTF mode, the engine operates on code point, so dot-all matches any code point except for newline sequences. The dot-all mode is called `PCRE_DOTALL`.

**PHP**: PCRE, compiled as UTF-8 library and `\n` is the only newline sequence by default. Dot-all mode is accessible via `s` flag.

**Postgres**: In default mode, dot-all matches any code point without exception.

---

## Factoid

Ŗ͞e̡͟҉ǵ͟͢e̴̢͘͡x̡́͞ ̛̀҉҉̢c҉̷̨a̸̛͞n҉̛͠ ̷̸̀p̴͠͡҉̵ą̧͜͢r̸̸̷̢͝s̢̀͡e̷̷̷͘͞ ̨̧̀H̨̧͜͜T̷͞M̷̛͜L͢.̴̡́ Repeat after me. R̶̶̢̧̰̞̲̻̮̳̦̥ͭͯ́̓̎͂̈ͯͤ̇͊͊͟ĕ̱̹̩̪͈͈͍̗͎̝͚̽̈́ͨ̐̽ͪͮ̍͂͐ͮͧ̔̏̓ͣ̀ĝ̵̢̢̖̤̜̭͔͊͒ͦ͛ͤ͗ͬͧͪ̾͘͟eͦ̄ͭ̑̾҉̨̨̝̬̹̘̭͔͟͢x̣̻͓̠͈͕̥̜͚̱̝̫͚̳̾̍ͦ̑̈́̋̌̉̎͊ͮ͗̄̆̒́̚̚ͅ ̸̦͈̥̬̺͇͂ͧͧ̃͐̎ͮ̌ͤ̈́̒̆ͣ̈́̏̔͊̐̀ç̨̬̪̳̦͎̖͕̦͔ͨ̃̿̓̈́ͅȁ̸̳̺̠̭ͮ̎̓̐͘̕͜͡ņ̨̫͔͍̬̤̘͎͚̣̟̦͍̜ͭͭ̈́ͦ̈́̽͗ͥ̑͝͡ ̸̛̖̝̻̻͎̍̄ͭ̓ͨ̋͋̈́͗̌̇ͤ͋ͬ͘pͪ̒̍ͫͤͭ͊ͮ̇̿̆̐̄̎͌̚͏̧͏͇̼͚̰͓̲͕̰̖̘̟̞̺̲ḁ̛͇̫̻̉̊ͣͭͤ̇ͨ́͘͠rͦ̂̈́̆͑͊ͣ̊ͮ̉̉͆ͧ̒͛̐̋̚͏̴̭̫̞̯̘̖͍̼̖̜̞̖̩͕̹̻̮̗͜͡͞ͅs̟͈̺͖̦̟̙̦͖̤ͬ̋͌̄͂ͩ̓̐̔̓͌̾̀̈͊̊ͤ̀̚eͫ̐͒̽ͯͫͨ͏̨̡̦̤̙͍̙̪̝̮̤͎̭̖̪̻͙͍͖͉̀́ ͉̭̫̰͔̝͓̼̮͚̻͎͎͉̐͗͗͊̇ͣ͒͗͑̆͐̎̐̀ͬ͛ͮ͝H̢̥͕̼͓̫͙̺̼̮ͣͦ̍ͨ͒̔̌T̪̲̦̻̦͖̞̤͒̑ͭ̐̑̃ͭͣ͐̎̒̉͊̀͜͜M̞̪͇͕̩͉͗ͧ̌ͯ͋͂̉̍ͭ̓̇̐̌͜͠Ĺ̷̨̳̘̯͚͓͛͌ͭ̉̍.ͯ͆̊̌ͯ̇̓̏͐ͪ̋̈́͑̕҉̷̠̰̼̤̲̀́