rug 0.4.0

Arbitrary-precision big numbers based on GMP, MPFR and MPC
Documentation 
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// Copyright © 2017 University of Malta

// This program is free software: you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License
// as published by the Free Software Foundation, either version 3 of
// the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License and a copy of the GNU General Public License along with
// this program. If not, see <http://www.gnu.org/licenses/>.

use gmp_mpfr_sys::gmp::{self, mpq_t};
use std::mem;
use std::os::raw::{c_long, c_ulong};

pub unsafe fn mpq_inv_check_0(rop: *mut mpq_t, op: *const mpq_t) {
    assert_ne!(gmp::mpq_sgn(op), 0, "division by zero");
    gmp::mpq_inv(rop, op);
}

pub unsafe fn mpq_mul_2exp_si(rop: *mut mpq_t, op1: *const mpq_t, op2: c_long) {
    if op2 >= 0 {
        gmp::mpq_mul_2exp(rop, op1, op2 as c_ulong);
    } else {
        gmp::mpq_div_2exp(rop, op1, op2.wrapping_neg() as c_ulong);
    }
}

pub unsafe fn mpq_div_2exp_si(rop: *mut mpq_t, op1: *const mpq_t, op2: c_long) {
    if op2 >= 0 {
        gmp::mpq_div_2exp(rop, op1, op2 as c_ulong);
    } else {
        gmp::mpq_mul_2exp(rop, op1, op2.wrapping_neg() as c_ulong);
    }
}

pub unsafe fn mpq_pow_ui(rop: *mut mpq_t, op1: *const mpq_t, op2: c_ulong) {
    let rop_num = gmp::mpq_numref(rop);
    let rop_den = gmp::mpq_denref(rop);
    let op1_num = gmp::mpq_numref(op1 as *mut _) as *const _;
    let op1_den = gmp::mpq_denref(op1 as *mut _) as *const _;
    gmp::mpz_pow_ui(rop_num, op1_num, op2);
    gmp::mpz_pow_ui(rop_den, op1_den, op2);
}

pub unsafe fn mpq_pow_si(rop: *mut mpq_t, op1: *const mpq_t, op2: c_long) {
    if op2 < 0 {
        assert_ne!(gmp::mpq_sgn(op1), 0, "division by zero");
        gmp::mpq_inv(rop, op1);
        mpq_pow_ui(rop, rop, op2.wrapping_neg() as c_ulong);
    } else {
        mpq_pow_ui(rop, op1, op2 as c_ulong);
    };
}

pub unsafe fn mpq_ceil(rop: *mut gmp::mpz_t, op: *const mpq_t) {
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    if gmp::mpz_cmp_ui(denref, 1) == 0 {
        gmp::mpz_set(rop, numref);
    } else {
        gmp::mpz_tdiv_q(rop, numref, denref);
        if gmp::mpz_sgn(numref) > 0 {
            gmp::mpz_add_ui(rop, rop, 1);
        }
    }
}

pub unsafe fn mpq_floor(rop: *mut gmp::mpz_t, op: *const mpq_t) {
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    if gmp::mpz_cmp_ui(denref, 1) == 0 {
        gmp::mpz_set(rop, numref);
    } else {
        gmp::mpz_tdiv_q(rop, numref, denref);
        if gmp::mpz_sgn(numref) < 0 {
            gmp::mpz_sub_ui(rop, rop, 1);
        }
    }
}

pub unsafe fn mpq_round(rop: *mut gmp::mpz_t, op: *const mpq_t) {
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    if gmp::mpz_cmp_ui(denref, 1) == 0 {
        gmp::mpz_set(rop, numref);
    } else {
        // The remainder cannot be larger than the divisor, but we
        // allocate an extra limb because the GMP docs say we should,
        // and we have to multiply by 2.
        let bits = ((*denref).size.abs() + 1) * gmp::LIMB_BITS;
        let mut rem: gmp::mpz_t = mem::uninitialized();
        gmp::mpz_init2(&mut rem, bits as gmp::bitcnt_t);
        gmp::mpz_tdiv_qr(rop, &mut rem, numref, denref);
        // if 2 * abs(rem) >= divisor, move one away from zero
        gmp::mpz_abs(&mut rem, &rem);
        gmp::mpz_mul_2exp(&mut rem, &rem, 1);
        if gmp::mpz_cmp(&rem, denref) >= 0 {
            if gmp::mpz_sgn(numref) > 0 {
                gmp::mpz_add_ui(rop, rop, 1);
            } else {
                gmp::mpz_sub_ui(rop, rop, 1);
            }
        }
        gmp::mpz_clear(&mut rem);
    }
}

pub unsafe fn mpq_trunc(rop: *mut gmp::mpz_t, op: *const mpq_t) {
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    gmp::mpz_tdiv_q(rop, numref, denref);
}

pub unsafe fn mpq_fract(rop: *mut mpq_t, op: *const mpq_t) {
    let r_numref = gmp::mpq_numref(rop);
    let r_denref = gmp::mpq_denref(rop);
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    gmp::mpz_tdiv_r(r_numref, numref, denref);
    gmp::mpz_set(r_denref, denref);
}

pub unsafe fn mpq_fract_trunc(
    fop: *mut mpq_t,
    top: *mut gmp::mpz_t,
    op: *const mpq_t,
) {
    let f_numref = gmp::mpq_numref(fop);
    let f_denref = gmp::mpq_denref(fop);
    let numref = gmp::mpq_numref(op as *mut _) as *const _;
    let denref = gmp::mpq_denref(op as *mut _) as *const _;
    gmp::mpz_tdiv_qr(top, f_numref, numref, denref);
    gmp::mpz_set(f_denref, denref);
}