Get negative numbers from expression

Question

I'm trying to separate the tokens on a string expression. The expression looks like this:

-1-2+-3

This is the regex I'm using:

[\d\.]+|[-][\d\.]+|\+|\-|\*|\/|\^|\(|\)

This brings me these matches:

-1
-2
+
-3

I was expecting:

-1
-
2
+
-3

Any ideas how can I distinct negative numbers from operators?

Answer 1

Maybe you could try this one; it makes use of a look-behind:

((?<=\d)[+*\/^()-]|\-?[\d.]+)

I tested it here.

Basically, makes sure that there is a number before the operator to decide what to match. So, if there is a digit before the operator, treat the operator alone, otherwise, combine the minus with the digit.

EDIT: Separated the brackets from the lot, just in case (demo):

((?<=\d)[+*\/^-]|[()]|\-?[\d.]+)