How to create a regex to validate user expression that includes some commands?

Question

I need to validate a user input that can include parentheses, the word 'or' and the word 'and'.

The rules are simple:

1- Parentheses can be used anywhere but opening parentheses must have closing one (I might validate this part with code). 2- The expression must never end with 'or' or 'and' within a block. For example:

John and Jane -> OK

John and -> NOT OK

(John and) -> NOT OK

John or -> NOT OK

(John or) -> NOT OK

So it always:

[Optional parentheses] WORD [Optional operation and or][Optional parentheses]

I came up with this but it's not enough but it's a start.

\b\w.*(?=or|and).*\w

That works for the content with parentheses

Note: I don't care about the amount of whitespace between words.

The user can combine these expression blocks multiple times.

Have a look at ^\w+(?:\s+(?:or|and)\s+\w+)*$. Instead of \w+, you can have (?:John|Jane). — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 7, 2016 at 16:13
If there must be optional parentheses: ^$?\w+(?:\s+(?:or|and)\s+\w+)*$?$. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 7, 2016 at 16:19

Will Barnwell · Accepted Answer · 2016-07-07 22:41:03Z

1

^\(?((\w+|\((?1)\))\s+(?>and|or)\s+(\w+|\((?1)\)))\)?$

I didn't think it could be done, but then I found recursion. https://regex101.com/r/aD7dT0/4

EDIT 1: This was broken, fixed it

EDIT 2: Made a better regex + it does parenthesis validation, with the exception of parenthesis around the entire statement

edited Jul 7, 2016 at 22:41

answered Jul 7, 2016 at 21:39

Will Barnwell

4,10924 silver badges34 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Will Barnwell Over a year ago

Im going to clean this up, its pretty gross as of regex101.com/r/aD7dT0/2

Will Barnwell Over a year ago

TIL all about regex recursion, shoutout to the regex debugger on regex101

code-gijoe Over a year ago

Excellent work, did not think it could be done either, excellent!

Collectives™ on Stack Overflow

How to create a regex to validate user expression that includes some commands?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related