While hacking together a generator cut combining system for [Rivet](http://projects.hepforge.org/rivet/) I just got an enormously unhelpful error from g++, namely from Projection.cc:3: ../../include/Rivet/Cut.hh:76: error: `map' specified as declarator-id ../../include/Rivet/Cut.hh:76: error: two or more data types in declaration of `map' Fortunately I've seen this one before, though I couldn't remember at first. It turns out that that's C++ compiler error language for "you forgot the stupid semi-colon on the end of your inner class declaration". Another reason to relegate C++ to the garbage bin of history! Incidentally, I just discovered that Bjarn Stroustroup used to be at my college in Cambridge... hopefully I'll run into him at a dinner sometime and can bother him about his horrid creation. And why blog about such a tiny and tedious topic? Well, the [Google coverage of this issue](http://www.google.co.uk/search?q=%22two+or+more+data+types+in+declaration) could certainly do with being improved...