Mathematical numeric comparison

Description:

This patch gives you the possibility to have mathematical expressions in (both sides of) your numeric comparison conditions.

How:

Currently both sides of the comparator are cast to a float. Instead we'll evaluate the mathematical expression entered.
Non-allowed characters (anything but mathematical operators and digits) are stripped from the expression, after which it is evaluated.

Example:

If you want a condition to check if a node is e.g. older than one week, you logically would compare the current date with the node date plus one week expressed in seconds.

Text to compare:
[node:site-timestamp]
Greater than:
[node:mod-timestamp] + (7*24*60*60)

After replacing the tokens this (internally) gives us the comparison:

1210764328 > 1204761600 + (7*24*60*60)

Now we'll mathematically evaluate both sides and then do the comparison:

1210764328 > 1205366400

Notes:

Currently, invalid mathematical expressions (such as 2*4+) return zero.