Initialization and Assignment Functions
=======================================

   The functions for integer arithmetic assume that all integer objects
are initialized.  You do that by calling the function `mpz_init'.

 - Function: void mpz_init (mpz_t INTEGER)
     Initialize INTEGER with limb space and set the initial numeric
     value to 0.  Each variable should normally only be initialized
     once, or at least cleared out (using `mpz_clear') between each
     initialization.

   Here is an example of using `mpz_init':

     {
       mpz_t integ;
       mpz_init (integ);
       ...
       mpz_add (integ, ...);
       ...
       mpz_sub (integ, ...);
     
       /* Unless the program is about to exit, do ... */
       mpz_clear (integ);
     }

As you can see, you can store new values any number of times, once an
object is initialized.

 - Function: void mpz_clear (mpz_t INTEGER)
     Free the limb space occupied by INTEGER.  Make sure to call this
     function for all `mpz_t' variables when you are done with them.

 - Function: void * _mpz_realloc (mpz_t INTEGER, mp_size_t NEW_ALLOC)
     Change the limb space allocation to NEW_ALLOC limbs.  This
     function is not normally called from user code, but it can be used
     to give memory back to the heap, or to increase the space of a
     variable to avoid repeated automatic re-allocation.

 - Function: void mpz_array_init (mpz_t INTEGER_ARRAY[], size_t
          ARRAY_SIZE, mp_size_t FIXED_NUM_BITS)
     Allocate *fixed* limb space for all ARRAY_SIZE integers in
     INTEGER_ARRAY.  The fixed allocation for each integer in the array
     is enough to store FIXED_NUM_BITS.  If the fixed space will be
     insufficient for storing the result of a subsequent calculation,
     the result is unpredictable.

     This function is useful for decreasing the working set for some
     algorithms that use large integer arrays.

     There is no way to de-allocate the storage allocated by this
     function.  Don't call `mpz_clear'!