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Implement centered-quotient with new integer lib

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* libguile/integers.c (scm_integer_centered_quotient_ii)
(scm_integer_centered_quotient_iz, scm_integer_centered_quotient_zi)
(scm_integer_centered_quotient_zz): New internal functions.
* libguile/integers.h: Declare internal functions.
* libguile/numbers.c (scm_centered_quotient): Use the new functions.
(scm_i_bigint_centered_quotient): Remove unused helper.
This commit is contained in:
Andy Wingo 2021-12-13 10:23:42 +01:00
parent f8a92773ac
commit 0ccdf06c81
3 changed files with 144 additions and 138 deletions
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140
libguile/numbers.c
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@ -2111,7 +2111,6 @@ scm_i_exact_rational_truncate_divide (SCM x, SCM y, SCM *qp, SCM *rp)
}
static SCM scm_i_inexact_centered_quotient (double x, double y);
static SCM scm_i_bigint_centered_quotient (SCM x, SCM y);
static SCM scm_i_exact_rational_centered_quotient (SCM x, SCM y);
SCM_PRIMITIVE_GENERIC (scm_centered_quotient, "centered-quotient", 2, 0, 0,
@ -2129,58 +2128,16 @@ SCM_PRIMITIVE_GENERIC (scm_centered_quotient, "centered-quotient", 2, 0, 0,
"@end lisp")
#define FUNC_NAME s_scm_centered_quotient
{
if (SCM_LIKELY (SCM_I_INUMP (x)))
if (SCM_I_INUMP (x))
{
scm_t_inum xx = SCM_I_INUM (x);
if (SCM_LIKELY (SCM_I_INUMP (y)))
{
scm_t_inum yy = SCM_I_INUM (y);
if (SCM_UNLIKELY (yy == 0))
scm_num_overflow (s_scm_centered_quotient);
else
{
scm_t_inum qq = xx / yy;
scm_t_inum rr = xx % yy;
if (SCM_LIKELY (xx > 0))
{
if (SCM_LIKELY (yy > 0))
{
if (rr >= (yy + 1) / 2)
qq++;
}
else
{
if (rr >= (1 - yy) / 2)
qq--;
}
}
else
{
if (SCM_LIKELY (yy > 0))
{
if (rr < -yy / 2)
qq--;
}
else
{
if (rr < yy / 2)
qq++;
}
}
if (SCM_LIKELY (SCM_FIXABLE (qq)))
return SCM_I_MAKINUM (qq);
else
return scm_i_inum2big (qq);
}
}
if (SCM_I_INUMP (y))
return scm_integer_centered_quotient_ii (SCM_I_INUM (x),
SCM_I_INUM (y));
else if (SCM_BIGP (y))
{
/* Pass a denormalized bignum version of x (even though it
can fit in a fixnum) to scm_i_bigint_centered_quotient */
return scm_i_bigint_centered_quotient (scm_i_long2big (xx), y);
}
return scm_integer_centered_quotient_iz (SCM_I_INUM (x), y);
else if (SCM_REALP (y))
return scm_i_inexact_centered_quotient (xx, SCM_REAL_VALUE (y));
return scm_i_inexact_centered_quotient (SCM_I_INUM (x),
SCM_REAL_VALUE (y));
else if (SCM_FRACTIONP (y))
return scm_i_exact_rational_centered_quotient (x, y);
else
@ -2189,44 +2146,10 @@ SCM_PRIMITIVE_GENERIC (scm_centered_quotient, "centered-quotient", 2, 0, 0,
}
else if (SCM_BIGP (x))
{
if (SCM_LIKELY (SCM_I_INUMP (y)))
{
scm_t_inum yy = SCM_I_INUM (y);
if (SCM_UNLIKELY (yy == 0))
scm_num_overflow (s_scm_centered_quotient);
else if (SCM_UNLIKELY (yy == 1))
return x;
else
{
SCM q = scm_i_mkbig ();
scm_t_inum rr;
/* Arrange for rr to initially be non-positive,
because that simplifies the test to see
if it is within the needed bounds. */
if (yy > 0)
{
rr = - mpz_cdiv_q_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (x), yy);
scm_remember_upto_here_1 (x);
if (rr < -yy / 2)
mpz_sub_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (q), 1);
}
else
{
rr = - mpz_cdiv_q_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (x), -yy);
scm_remember_upto_here_1 (x);
mpz_neg (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (q));
if (rr < yy / 2)
mpz_add_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (q), 1);
}
return scm_i_normbig (q);
}
}
if (SCM_I_INUMP (y))
return scm_integer_centered_quotient_zi (x, SCM_I_INUM (y));
else if (SCM_BIGP (y))
return scm_i_bigint_centered_quotient (x, y);
return scm_integer_centered_quotient_zz (x, y);
else if (SCM_REALP (y))
return scm_i_inexact_centered_quotient
(scm_i_big2dbl (x), SCM_REAL_VALUE (y));
@ -2276,49 +2199,6 @@ scm_i_inexact_centered_quotient (double x, double y)
return scm_nan ();
}
/* Assumes that both x and y are bigints, though
x might be able to fit into a fixnum. */
static SCM
scm_i_bigint_centered_quotient (SCM x, SCM y)
{
SCM q, r, min_r;
/* Note that x might be small enough to fit into a
fixnum, so we must not let it escape into the wild */
q = scm_i_mkbig ();
r = scm_i_mkbig ();
/* min_r will eventually become -abs(y)/2 */
min_r = scm_i_mkbig ();
mpz_tdiv_q_2exp (SCM_I_BIG_MPZ (min_r),
SCM_I_BIG_MPZ (y), 1);
/* Arrange for rr to initially be non-positive,
because that simplifies the test to see
if it is within the needed bounds. */
if (mpz_sgn (SCM_I_BIG_MPZ (y)) > 0)
{
mpz_cdiv_qr (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (r),
SCM_I_BIG_MPZ (x), SCM_I_BIG_MPZ (y));
scm_remember_upto_here_2 (x, y);
mpz_neg (SCM_I_BIG_MPZ (min_r), SCM_I_BIG_MPZ (min_r));
if (mpz_cmp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (min_r)) < 0)
mpz_sub_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (q), 1);
}
else
{
mpz_fdiv_qr (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (r),
SCM_I_BIG_MPZ (x), SCM_I_BIG_MPZ (y));
scm_remember_upto_here_2 (x, y);
if (mpz_cmp (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (min_r)) < 0)
mpz_add_ui (SCM_I_BIG_MPZ (q),
SCM_I_BIG_MPZ (q), 1);
}
scm_remember_upto_here_2 (r, min_r);
return scm_i_normbig (q);
}
static SCM
scm_i_exact_rational_centered_quotient (SCM x, SCM y)
{