5.1 Initialization Functions

The functions for integer arithmetic assume that all integer objects are initialized. You do that by calling the function mpz_init. For example,

{
  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_init (mpz_t x)

Initialize x, and set its value to 0.

Function: void mpz_inits (mpz_t x, ...)

Initialize a NULL-terminated list of mpz_t variables, and set their values to 0.

Function: void mpz_init2 (mpz_t x, mp_bitcnt_t n)

Initialize x, with space for n-bit numbers, and set its value to 0. Calling this function instead of mpz_init or mpz_inits is never necessary; reallocation is handled automatically by GMP when needed.

n is only the initial space, x will grow automatically in the normal way, if necessary, for subsequent values stored. mpz_init2 makes it possible to avoid such reallocations if a maximum size is known in advance.

Function: void mpz_clear (mpz_t x)

Free the space occupied by x. Call this function for all mpz_t variables when you are done with them.

Function: void mpz_clears (mpz_t x, ...)

Free the space occupied by a NULL-terminated list of mpz_t variables.

Function: void mpz_realloc2 (mpz_t x, mp_bitcnt_t n)

Change the space allocated for x to n bits. The value in x is preserved if it fits, or is set to 0 if not.

Calling this function is never necessary; reallocation is handled automatically by GMP when needed. But this function can be used to increase the space for a variable in order to avoid repeated automatic reallocations, or to decrease it to give memory back to the heap.

This document was generated on February 16, 2012 using texi2html 5.0.