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(gmp.info)C++ Interface General

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C++ Interface General
=====================

All the C++ classes and functions are available with

     #include <gmpxx.h>

The classes defined are

 - Class: mpz_class
 - Class: mpq_class
 - Class: mpf_class

   The standard operators and various standard functions are overloaded
to allow arithmetic with these classes.  For example,

     int
     main (void)
     {
       mpz_class a, b, c;
     
       a = 1234;
       b = "-5678";
       c = a+b;
       cout << "sum is " << c << "\n";
       cout << "absolute value is " << abs(c) << "\n";
     
       return 0;
     }

   An important feature of the implementation is that an expression like
`a=b+c' results in a single call to the corresponding `mpz_add',
without using a temporary for the `b+c' part.  Expressions which by
their nature imply intermediate values, like `a=b*c+d*e', still use
temporaries though.

   The classes can be freely intermixed in expressions, as can the
classes and the standard C++ types.

   Conversions back from the classes to standard C++ types aren't done
automatically, instead member functions like `get_si' are provided (see
the following sections for details).

   Also there are no automatic conversions from the classes to the
corresponding GMP C types, instead a reference to the underlying C
object can be obtained with the following functions,

 - Function: mpz_t mpz_class::get_mpz_t ()
 - Function: mpq_t mpq_class::get_mpq_t ()
 - Function: mpf_t mpf_class::get_mpf_t ()

   These can be used to call a C function which doesn't have a C++ class
interface.  For example to set `a' to the GCD of `b' and `c',

     mpz_class a, b, c;
     ...
     mpz_gcd (a.get_mpz_t(), b.get_mpz_t(), c.get_mpz_t());

   In the other direction, a class can be initialized from the
corresponding GMP C type, or assigned to if an explicit constructor is
used.  In both cases this makes a copy of the value, it doesn't create
any sort of association.  For example,

     mpz_t z;
     // ... init and calculate z ...
     mpz_class x(z);
     mpz_class y;
     y = mpz_class (z);

   There are no namespace setups in `gmpxx.h', all types and functions
are simply put into the global namespace.  This is what `gmp.h' has
done in the past, and continues to do for compatibility.  The extras
provided by `gmpxx.h' follow GMP naming conventions and are unlikely to
clash with anything.