Choosing between mpf_class and double at compile time

Pasquale Tricarico tricaric at
Thu Feb 26 11:25:09 CET 2009


This is my first post, but I have been using GMP for more than 5
years. I have a fair size C++ project that makes heavy use of
mpf_class, and for performance and testing reasons I would like to
have the possibility to switch between mpf_class and plain double at
compile time. In my code I have:

typedef mpf_class Double;

and then I always refer to Double in my code. This works really well,
but now if I want to switch to double, replacing the above typedef
with the following one is not enough of course:

typedef double Double;

This doesn't work because of all the methods I already call in the
code, such as Double::get_mpf_t(), conversions from/to mpz_class,
printing using gmp_printf("%Ff..."), and probably for a few more
reasons I haven't bumped into yet. Subclassing from double is not
possible as double is not a C++ class but just a type. One approach
could be to fill the code with macro switches such as:

#ifdef USE_GMP

But this would severely degrade the code. So I was wondering if anyone
here on the list has a good solution to switch between mpf_class and
double the smart way, staying away from evil macros. Thanks a lot.


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