Regexle (regexle.ithea.de)
Rate itFind today's secret regular expression by testing words against it.
Every day: One secret regular expression a day, the same for every player, taken in turn from a fixed list that began on May 15, 2024; links made with Create new puzzle play other patterns. New puzzle: Midnight local time.
Regexle hides a regular expression and lets you test any string to see whether it matches. When you think you know the pattern, you type a regex guess; a wrong guess earns a counterexample. It starts you off with one word that matches and one that does not.
About Regexle (regexle.ithea.de)
Regexle turns regular expressions into a guessing game. The page hides one pattern a day and gives you a matching word and a non-matching word to start. You type any character sequence into the test box, and it joins the green list of matches or the red list of non-matches. The worked example on the page shows the idea: banana, guacamole and macadamia match while cucumber, raspberry and peas do not, so the rule is two a's with one character between them, a.a.
When you are ready, you press the button and type your regex. If it is not equivalent to the secret one on the game's dictionary, you get a counterexample, a word your guess and the secret disagree on, and you carry on testing. The day's patterns range from a single letter class to backreferences that repeat a group, and a cheat sheet beside the board lists the symbols you need.
The game is made by @blinry and @piko with help from other contributors, and its source is on GitLab. Besides the daily pattern you can type your own regex to create a puzzle link for friends. It suits programmers and anyone curious about pattern rules. It is a different game from the hexagonal regex crossword at regexle.com.
How to play Regexle (regexle.ithea.de)
- Open regexle.ithea.de; the day's secret pattern is loaded, with one matching and one non-matching word shown.
- Type a word or any string into the test box and press the arrow to see whether it matches.
- Look at what the green matches share and what the red non-matches lack.
- Press I'm ready to guess a regex and type your pattern.
- If you are wrong, use the counterexample you are given and keep testing until your regex is accepted, or press Give up.
Tips
- Test short strings, single letters and odd characters as well as words: they narrow the rule fast.
- Remember anchors: if the rule is about the start or end, your guess needs ^ or $.
- A guess only has to match the same dictionary words as the answer, not be written the same way.
- Keep the cheat sheet open: backreferences like \1 turn up on harder days.
Questions
Do I need to know regular expressions?
Some basics help. The page has a cheat sheet of the symbols used, with examples.
What happens if my regex guess is wrong?
You get a counterexample: a word that one pattern matches and the other does not.
Is it the same as regexle.com?
No. regexle.com is a hexagonal regex crossword; this Regexle hides one pattern for you to discover by testing strings.
Can I make my own puzzle?
Yes, Create new puzzle turns any regex you enter into a link you can share.
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