is this possible somehow? I can't find any solution.

you whould somehow have to define string to the variable, like a type.
though string is a set of bytes, ending with 0 , $ , or starting with length
from this, nearly anything could be string, even a x: dw 2113
since there is not a type "string" in fasm, like in c

so technically, when you pass string, you pass an address, so you can pass anything as string

no, there is type string constant - one enclosed in "" and ''. This is one i would like to determine

Does that not work? Or did I miss something.

No, you cannot determine that at preprocessor stage. With "match" you can only check for the literally the same quoted string.

too bad, more overhead for assembler then.

This would be also solved with parse-time evalutating of predicatable ifs (if 'aaaa' eqtyoe ''). Have you already been planning something more this way?

I've been planning it, however only partial solution is possible - that is, replacing the <if 'aaaa' eqtype ''> with <if 1> during the parsing, etc.