Folks we have a problem: rather late in the day I've discovered that our Math.Constants code doesn't compile on anything except VC++, and the problem is preprocessor token pasting. So I'm hoping we have some experts around here that can help! The issue is we currently construct the constants from a macro invocation such as: BOOST_DEFINE_MATH_CONSTANT(half, 5.000000000000000000000000000000000000, 00000000000000000000000000000000000000000000000000000000000000000000000000, -01); But the "-01" part (the exponent) isn't a valid pp-token, so trying to token-paste it fails on GCC (compiler error). Does anyone know if there's a way to overcome this? As an alternative, I've considered something like: BOOST_DEFINE_MATH_CONSTANT(ln_two, 6.931471805599453094172321214581765680e-001, "6.93147180559945309417232121458176568075500134360255254120680009493393621969694715605863326996418687542001481021e-001"); But this would still require token pasting of the 6.931471805599453094172321214581765680e-001 part. But is this now a valid pp-token if the "-" is internal to the token? It works on the compilers I've tried, but I don't want to be skewered by this again down the line.... Truly hating the preprocessor yours, John.