Finding a suitable math parser

GSPC currently uses spar-0.5.10, a quite nice math language parser. However, it is unmaintained, still contains a lot of bugs and is incomplete. Can anybody tell me why in this big world of free software there is not a single simple mathematical parser that can be embedded into an application? I just want to evaluate simple statements like "(X*3.56)-max(y*1.23,z*1.341)".

The author of spar has since started a new project, called Iguana. It is a whole language, not only simple mathematical statements. However, it still lacks some of the functionality spar used to have - and it has a totally different syntax.

Now I face the choice between extending the good old spar with stuff like variable length argument functions, or convert everything to use Iguana (and implement the missing bits from spar in Iguana).