Working on evaluation

I have been working on evaluation the past few days. Not the evaluation of the SoC, this is something I am going to do that next Monday, but that of PHP. The reason for this evaluation can be found in the first blog of Monday.

There is currently support for arithmetic operators on the following types: integer, float, Boolean, null and string. Types can also be juggled to an other type. It took some time to get this juggling right. Especially the juggling from String to numbers. The string is now sort of parsed within Stratego to get the part that can be recognized as a integer / float. But it works :)