Regular expression for floats with a fixed number of significant digits

Question

I'm trying to find a regular expression for a float with a fixed maximum (for example 4) number of significant figures.

this should match with:

- 123.4
- 12.34
- 1.2
- 223
- 0.1234
- 0.000001234

the problem is that the number of non-zeros before and after the dot has to be at most 4 in total.

I tried to split the problem and found solutions for the cases:

- 0.xxxx
- 0.000xxx
- xxxx

But I didn't find a solution for the case that significant digits are found before and after the dot. (examples: 1.23 2.345 )

update: I think I found a solution:

^(?!(?:.*[1-9](\.?[0-9]){4,}))([-+]?\d+\.?\d*?)$

yes, i allow .23 and 65. if that makes the problem more easy. — user4116042, Oct 07 '14 at 13:15
`/([1-9]+([0-9]+)?)?\.(([1-9])|(0+[1-9]+))/g` will match all significant digits (not answering your question, specifically, just thought it might be helpful) — Cplusplusplus, Jan 16 '18 at 20:56

score 1 · Accepted Answer · answered Oct 07 '14 at 08:16

1

^(?!(?:.*?[1-9]){5,})([-+]?\s*\d+\.?\d*?)$

Try this.This will match only 4 or less significant digits.Do not forget to put flags g and m.See demo.

answered Oct 07 '14 at 08:16

vks

thanks! this is not exactly what I need because for example 122.04 is also matched but has 5 significant digits. But the use of a negative lookahead is a good hint! – user4116042 Oct 07 '14 at 12:49

Avinash Raj · Answer 2 · 2014-10-07T13:16:24.180

0

I think you want something like this,

^0*(?:[1-9]\d{0,3})?(?:\.0*(?:[1-9]\d{0,3})?)?$

edited Oct 07 '14 at 13:16

answered Oct 07 '14 at 08:57

Avinash Raj

ok! but 0000.0000000012340 is also matched but has 5 sign. digits – user4116042 Oct 07 '14 at 13:00
sorry i don't know what do you mean. did you want to allow `100000.00001` – Avinash Raj Oct 07 '14 at 13:02
sorry, i don't allow that number because after the first non-zero ([1-9],the first digit) more than 4 digits [0-9] are printed. – user4116042 Oct 07 '14 at 13:13

2 Answers2