Way to tell in libcpp if something is a macro...

[Ed Smith-Rowland <3dw4rd at verizon dot net>]

Greetings,

I have a situation where I would like to detect if a string is a 
currently defined macro.

Something like a

  bool cpp_is_macro(const unsigned char *);

would be great.

Or perhaps I could construct something from the string and test that.

If something like this doesn't exist does anyone have some pointers on 
how to make one for libcpp.

Thanks.