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/*
Copyright (C) 2014 Fredrik Johansson
This file is part of Arb.
Arb is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "mag.h"
void
mag_expm1(mag_t y, const mag_t x)
{
if (mag_is_special(x))
{
if (mag_is_zero(x))
mag_zero(y);
else
mag_inf(y);
}
else if (COEFF_IS_MPZ(MAG_EXP(x)))
{
if (fmpz_sgn(MAG_EXPREF(x)) > 0)
{
mag_inf(y);
}
else
{
fmpz_set(MAG_EXPREF(y), MAG_EXPREF(x));
MAG_MAN(y) = MAG_MAN(x) + 1;
MAG_ADJUST_ONE_TOO_LARGE(y);
}
}
else
{
slong e = MAG_EXP(x);
if (e <= -16)
{
fmpz_set(MAG_EXPREF(y), MAG_EXPREF(x));
if (e < -MAG_BITS)
MAG_MAN(y) = MAG_MAN(x) + 1;
else
MAG_MAN(y) = MAG_MAN(x) + (MAG_ONE_HALF >> 15);
MAG_ADJUST_ONE_TOO_LARGE(y);
}
else
{
mag_exp(y, x);
/* subtract 1 */
if (e < 6)
{
slong e2 = MAG_EXP(y);
unsigned int c;
if (e2 < MAG_BITS)
{
/* this is correct since exp(x) >= 1 */
MAG_MAN(y) -= (MAG_ONE_HALF >> (e2 - 1));
c = MAG_BITS - FLINT_BIT_COUNT(MAG_MAN(y));
MAG_MAN(y) <<= c;
MAG_EXP(y) -= c;
}
}
}
}
}
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