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Info Node: (gmp.info)Integer Division

(gmp.info)Integer Division


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Division Functions
==================

   Division is undefined if the divisor is zero.  Passing a zero
divisor to the division or modulo functions (including the modular
powering functions `mpz_powm' and `mpz_powm_ui'), will cause an
intentional division by zero.  This lets a program handle arithmetic
exceptions in these functions the same way as for normal C `int'
arithmetic.

 - Function: void mpz_cdiv_q (mpz_t Q, mpz_t N, mpz_t D)
 - Function: void mpz_cdiv_r (mpz_t R, mpz_t N, mpz_t D)
 - Function: void mpz_cdiv_qr (mpz_t Q, mpz_t R, mpz_t N, mpz_t D)
 - Function: unsigned long int mpz_cdiv_q_ui (mpz_t Q, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_cdiv_r_ui (mpz_t R, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_cdiv_qr_ui (mpz_t Q, mpz_t R,
          mpz_t N, unsigned long int D)
 - Function: unsigned long int mpz_cdiv_ui (mpz_t N,
          unsigned long int D)
 - Function: void mpz_cdiv_q_2exp (mpz_t Q, mpz_t N,
          unsigned long int B)
 - Function: void mpz_cdiv_r_2exp (mpz_t R, mpz_t N,
          unsigned long int B)

 - Function: void mpz_fdiv_q (mpz_t Q, mpz_t N, mpz_t D)
 - Function: void mpz_fdiv_r (mpz_t R, mpz_t N, mpz_t D)
 - Function: void mpz_fdiv_qr (mpz_t Q, mpz_t R, mpz_t N, mpz_t D)
 - Function: unsigned long int mpz_fdiv_q_ui (mpz_t Q, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_fdiv_r_ui (mpz_t R, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_fdiv_qr_ui (mpz_t Q, mpz_t R,
          mpz_t N, unsigned long int D)
 - Function: unsigned long int mpz_fdiv_ui (mpz_t N,
          unsigned long int D)
 - Function: void mpz_fdiv_q_2exp (mpz_t Q, mpz_t N,
          unsigned long int B)
 - Function: void mpz_fdiv_r_2exp (mpz_t R, mpz_t N,
          unsigned long int B)

 - Function: void mpz_tdiv_q (mpz_t Q, mpz_t N, mpz_t D)
 - Function: void mpz_tdiv_r (mpz_t R, mpz_t N, mpz_t D)
 - Function: void mpz_tdiv_qr (mpz_t Q, mpz_t R, mpz_t N, mpz_t D)
 - Function: unsigned long int mpz_tdiv_q_ui (mpz_t Q, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_tdiv_r_ui (mpz_t R, mpz_t N,
          unsigned long int D)
 - Function: unsigned long int mpz_tdiv_qr_ui (mpz_t Q, mpz_t R,
          mpz_t N, unsigned long int D)
 - Function: unsigned long int mpz_tdiv_ui (mpz_t N,
          unsigned long int D)
 - Function: void mpz_tdiv_q_2exp (mpz_t Q, mpz_t N,
          unsigned long int B)
 - Function: void mpz_tdiv_r_2exp (mpz_t R, mpz_t N,
          unsigned long int B)

     Divide N by D, forming a quotient Q and/or remainder R.  For the
     `2exp' functions, D=2^B.  The rounding is in three styles, each
     suiting different applications.

        * `cdiv' rounds Q up towards +infinity, and R will have the
          opposite sign to D.  The `c' stands for "ceil".

        * `fdiv' rounds Q down towards -infinity, and R will have the
          same sign as D.  The `f' stands for "floor".

        * `tdiv' rounds Q towards zero, and R will have the same sign
          as N.  The `t' stands for "truncate".

     In all cases Q and R will satisfy N=Q*D+R, and R will satisfy
     0<=abs(R)<abs(D).

     The `q' functions calculate only the quotient, the `r' functions
     only the remainder, and the `qr' functions calculate both.  Note
     that for `qr' the same variable cannot be passed for both Q and R,
     or results will be unpredictable.

     For the `ui' variants the return value is the remainder, and in
     fact returning the remainder is all the `div_ui' functions do.  For
     `tdiv' and `cdiv' the remainder can be negative, so for those the
     return value is the absolute value of the remainder.

     The `2exp' functions are right shifts and bit masks, but of course
     rounding the same as the other functions.  For positive N both
     `mpz_fdiv_q_2exp' and `mpz_tdiv_q_2exp' are simple bitwise right
     shifts.  For negative N, `mpz_fdiv_q_2exp' is effectively an
     arithmetic right shift treating N as twos complement the same as
     the bitwise logical functions do, whereas `mpz_tdiv_q_2exp'
     effectively treats N as sign and magnitude.

 - Function: void mpz_mod (mpz_t R, mpz_t N, mpz_t D)
 - Function: unsigned long int mpz_mod_ui (mpz_t R, mpz_t N,
          unsigned long int D)
     Set R to N `mod' D.  The sign of the divisor is ignored; the
     result is always non-negative.

     `mpz_mod_ui' is identical to `mpz_fdiv_r_ui' above, returning the
     remainder as well as setting R.  See `mpz_fdiv_ui' above if only
     the return value is wanted.

 - Function: void mpz_divexact (mpz_t Q, mpz_t N, mpz_t D)
 - Function: void mpz_divexact_ui (mpz_t Q, mpz_t N, unsigned long D)
     Set Q to N/D.  These functions produce correct results only when
     it is known in advance that D divides N.

     These routines are much faster than the other division functions,
     and are the best choice when exact division is known to occur, for
     example reducing a rational to lowest terms.

 - Function: int mpz_divisible_p (mpz_t N, mpz_t D)
 - Function: int mpz_divisible_ui_p (mpz_t N, unsigned long int D)
 - Function: int mpz_divisible_2exp_p (mpz_t N, unsigned long int B)
     Return non-zero if N is exactly divisible by D, or in the case of
     `mpz_divisible_2exp_p' by 2^B.

 - Function: int mpz_congruent_p (mpz_t N, mpz_t C, mpz_t D)
 - Function: int mpz_congruent_ui_p (mpz_t N, unsigned long int C,
          unsigned long int D)
 - Function: int mpz_congruent_2exp_p (mpz_t N, mpz_t C, unsigned long
          int B)
     Return non-zero if N is congruent to C modulo D, or in the case of
     `mpz_congruent_2exp_p' modulo 2^B.


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