Regular expression for checking decimal numbers

Question

The regular expression must meet the criteria below. The number of elements before and after the point can be any. Only 1 point is allowed, and a negative sign is allowed only in the first position. I don't need a comma.

Example:

1
-1
-1.
1.
1.2
-.2
-0.2
000.300

All the above expressions must be true.

So if I break ..

• Optional negative sign in the first place.
• Zero or more digits before the point.
• Point is optional. May reach a maximum once. It can also be a pure integer.
• O or more digits after the dot.

Any help would be appreciated.

Answer 1

What you might want is this:

^-?\d*\.?\d*

(-?),
(\d*),
(\.),
(\d*).

, float , @MarcinJuraszek , .

Answer 2

1) :

^:

-:

?:

2)

/d: digit

*: ( )

3)

.:

?:

4) 0

/d: digit

*: ( )

, : ^ -?/d *.?/d *

Answer 3

Here is my solution

Pros

• User can specify accuracy
• Take a comma or period
• Accept negative values
• Accept integers

vs

• not working for .0 or 0 .: (

  [-] \ d {1,18}? (?: [.,] \ D {1,2})? $