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Clean up scm_divide

* libguile/integers.h:
* libguile/integers.c (scm_is_integer_divisible_ii):
(scm_is_integer_divisible_zi):
(scm_is_integer_divisible_zz): New helpers.
* libguile/numbers.c (invert, divide, complex_div): New helpers for
scm_divide.
(scm_divide): Adapt.
This commit is contained in:
Andy Wingo 2022-01-04 22:32:27 +01:00
parent 3e08c9cec0
commit 8b2d58b993
3 changed files with 326 additions and 297 deletions

View file

@ -2658,3 +2658,88 @@ scm_integer_mul_zz (struct scm_bignum *x, struct scm_bignum *y)
scm_remember_upto_here_2 (x, y);
return take_mpz (result);
}
int
scm_is_integer_divisible_ii (scm_t_inum x, scm_t_inum y)
{
ASSERT (y != 0);
return (x % y) == 0;
}
int
scm_is_integer_divisible_zi (struct scm_bignum *x, scm_t_inum y)
{
ASSERT (y != 0);
switch (y)
{
case -1:
case 1:
return 1;
default:
{
scm_t_inum abs_y = y < 0 ? -y : y;
mpz_t zx;
alias_bignum_to_mpz (x, zx);
int divisible = mpz_divisible_ui_p (zx, abs_y);
scm_remember_upto_here_1 (x);
return divisible;
}
}
}
int
scm_is_integer_divisible_zz (struct scm_bignum *x, struct scm_bignum *y)
{
mpz_t zx, zy;
alias_bignum_to_mpz (x, zx);
alias_bignum_to_mpz (y, zy);
int divisible_p = mpz_divisible_p (zx, zy);
scm_remember_upto_here_2 (x, y);
return divisible_p;
}
SCM
scm_integer_exact_quotient_ii (scm_t_inum n, scm_t_inum d)
{
return scm_integer_truncate_quotient_ii (n, d);
}
/* Return the exact integer q such that n = q*d, for exact integers n
and d, where d is known in advance to divide n evenly (with zero
remainder). For large integers, this can be computed more
efficiently than when the remainder is unknown. */
SCM
scm_integer_exact_quotient_zi (struct scm_bignum *n, scm_t_inum d)
{
if (SCM_UNLIKELY (d == 0))
scm_num_overflow ("quotient");
else if (SCM_UNLIKELY (d == 1))
return scm_from_bignum (n);
mpz_t q, zn;
mpz_init (q);
alias_bignum_to_mpz (n, zn);
if (d > 0)
mpz_divexact_ui (q, zn, d);
else
{
mpz_divexact_ui (q, zn, -d);
mpz_neg (q, q);
}
scm_remember_upto_here_1 (n);
return take_mpz (q);
}
SCM
scm_integer_exact_quotient_zz (struct scm_bignum *n, struct scm_bignum *d)
{
mpz_t q, zn, zd;
mpz_init (q);
alias_bignum_to_mpz (n, zn);
alias_bignum_to_mpz (d, zd);
mpz_divexact (q, zn, zd);
scm_remember_upto_here_2 (n, d);
return take_mpz (q);
}

View file

@ -184,6 +184,18 @@ SCM_INTERNAL SCM scm_integer_mul_ii (scm_t_inum x, scm_t_inum y);
SCM_INTERNAL SCM scm_integer_mul_zi (struct scm_bignum *x, scm_t_inum y);
SCM_INTERNAL SCM scm_integer_mul_zz (struct scm_bignum *x, struct scm_bignum *y);
SCM_INTERNAL int scm_is_integer_divisible_ii (scm_t_inum x, scm_t_inum y);
SCM_INTERNAL int scm_is_integer_divisible_zi (struct scm_bignum *x,
scm_t_inum y);
SCM_INTERNAL int scm_is_integer_divisible_zz (struct scm_bignum *x,
struct scm_bignum *y);
SCM_INTERNAL SCM scm_integer_exact_quotient_ii (scm_t_inum n, scm_t_inum d);
SCM_INTERNAL SCM scm_integer_exact_quotient_zi (struct scm_bignum *n,
scm_t_inum d);
SCM_INTERNAL SCM scm_integer_exact_quotient_zz (struct scm_bignum *n,
struct scm_bignum *d);
#endif /* SCM_INTEGERS_H */

View file

@ -5576,44 +5576,16 @@ arising out of or in connection with the use or performance of
this software.
****************************************************************/
SCM_PRIMITIVE_GENERIC (scm_i_divide, "/", 0, 2, 1,
(SCM x, SCM y, SCM rest),
"Divide the first argument by the product of the remaining\n"
"arguments. If called with one argument @var{z1}, 1/@var{z1} is\n"
"returned.")
#define FUNC_NAME s_scm_i_divide
static SCM
invert (SCM x)
{
while (!scm_is_null (rest))
{ x = scm_divide (x, y);
y = scm_car (rest);
rest = scm_cdr (rest);
}
return scm_divide (x, y);
}
#undef FUNC_NAME
#define s_divide s_scm_i_divide
#define g_divide g_scm_i_divide
SCM
scm_divide (SCM x, SCM y)
#define FUNC_NAME s_divide
if (SCM_I_INUMP (x))
switch (SCM_I_INUM (x))
{
double a;
if (SCM_UNLIKELY (SCM_UNBNDP (y)))
{
if (SCM_UNBNDP (x))
return scm_wta_dispatch_0 (g_divide, s_divide);
else if (SCM_I_INUMP (x))
{
scm_t_inum xx = SCM_I_INUM (x);
if (xx == 1 || xx == -1)
return x;
else if (xx == 0)
scm_num_overflow (s_divide);
else
return scm_i_make_ratio_already_reduced (SCM_INUM1, x);
case -1: return x;
case 0: scm_num_overflow ("divide");
case 1: return x;
default: return scm_i_make_ratio_already_reduced (SCM_INUM1, x);
}
else if (SCM_BIGP (x))
return scm_i_make_ratio_already_reduced (SCM_INUM1, x);
@ -5640,39 +5612,11 @@ scm_divide (SCM x, SCM y)
return scm_i_make_ratio_already_reduced (SCM_FRACTION_DENOMINATOR (x),
SCM_FRACTION_NUMERATOR (x));
else
return scm_wta_dispatch_1 (g_divide, x, SCM_ARG1, s_divide);
abort (); /* Unreachable. */
}
if (SCM_LIKELY (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 (yy == 0)
scm_num_overflow (s_divide);
else if (xx % yy != 0)
return scm_i_make_ratio (x, y);
else
{
scm_t_inum z = xx / yy;
if (SCM_FIXABLE (z))
return SCM_I_MAKINUM (z);
else
return scm_i_inum2big (z);
}
}
else if (SCM_BIGP (y))
return scm_i_make_ratio (x, y);
else if (SCM_REALP (y))
/* FIXME: Precision may be lost here due to:
(1) The cast from 'scm_t_inum' to 'double'
(2) Double rounding */
return scm_i_from_double ((double) xx / SCM_REAL_VALUE (y));
else if (SCM_COMPLEXP (y))
{
a = xx;
complex_div: /* y _must_ be a complex number */
static SCM
complex_div (double a, SCM y)
{
double r = SCM_COMPLEX_REAL (y);
double i = SCM_COMPLEX_IMAG (y);
@ -5689,146 +5633,106 @@ scm_divide (SCM x, SCM y)
return scm_c_make_rectangular (a / d, -(a * t) / d);
}
}
}
static SCM
divide (SCM x, SCM y)
{
if (scm_is_eq (y, SCM_INUM0))
scm_num_overflow ("divide");
if (SCM_I_INUMP (x))
{
if (scm_is_eq (x, SCM_INUM1))
return invert (y);
if (SCM_I_INUMP (y))
return scm_is_integer_divisible_ii (SCM_I_INUM (x), SCM_I_INUM (y))
? scm_integer_exact_quotient_ii (SCM_I_INUM (x), SCM_I_INUM (y))
: scm_i_make_ratio (x, y);
else if (SCM_BIGP (y))
return scm_i_make_ratio (x, y);
else if (SCM_REALP (y))
/* FIXME: Precision may be lost here due to:
(1) The cast from 'scm_t_inum' to 'double'
(2) Double rounding */
return scm_i_from_double ((double) SCM_I_INUM (x) / SCM_REAL_VALUE (y));
else if (SCM_COMPLEXP (y))
return complex_div (SCM_I_INUM (x), y);
else if (SCM_FRACTIONP (y))
/* a / b/c = ac / b */
return scm_i_make_ratio (scm_product (x, SCM_FRACTION_DENOMINATOR (y)),
SCM_FRACTION_NUMERATOR (y));
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARGn, s_divide);
abort (); /* Unreachable. */
}
else if (SCM_BIGP (x))
{
if (SCM_I_INUMP (y))
{
scm_t_inum yy = SCM_I_INUM (y);
if (yy == 0)
scm_num_overflow (s_divide);
else if (yy == 1)
return x;
else
{
/* FIXME: HMM, what are the relative performance issues here?
We need to test. Is it faster on average to test
divisible_p, then perform whichever operation, or is it
faster to perform the integer div opportunistically and
switch to real if there's a remainder? For now we take the
middle ground: test, then if divisible, use the faster div
func. */
scm_t_inum abs_yy = yy < 0 ? -yy : yy;
int divisible_p = mpz_divisible_ui_p (SCM_I_BIG_MPZ (x), abs_yy);
if (divisible_p)
{
SCM result = scm_i_mkbig ();
mpz_divexact_ui (SCM_I_BIG_MPZ (result), SCM_I_BIG_MPZ (x), abs_yy);
scm_remember_upto_here_1 (x);
if (yy < 0)
mpz_neg (SCM_I_BIG_MPZ (result), SCM_I_BIG_MPZ (result));
return scm_i_normbig (result);
}
else
return scm_i_make_ratio (x, y);
}
}
return scm_is_integer_divisible_zi (scm_bignum (x), SCM_I_INUM (y))
? scm_integer_exact_quotient_zi (scm_bignum (x), SCM_I_INUM (y))
: scm_i_make_ratio (x, y);
else if (SCM_BIGP (y))
{
int divisible_p = mpz_divisible_p (SCM_I_BIG_MPZ (x),
SCM_I_BIG_MPZ (y));
if (divisible_p)
{
SCM result = scm_i_mkbig ();
mpz_divexact (SCM_I_BIG_MPZ (result),
SCM_I_BIG_MPZ (x),
SCM_I_BIG_MPZ (y));
scm_remember_upto_here_2 (x, y);
return scm_i_normbig (result);
}
else
return scm_i_make_ratio (x, y);
}
return scm_is_integer_divisible_zz (scm_bignum (x), scm_bignum (y))
? scm_integer_exact_quotient_zz (scm_bignum (x), scm_bignum (y))
: scm_i_make_ratio (x, y);
else if (SCM_REALP (y))
/* FIXME: Precision may be lost here due to:
(1) scm_i_big2dbl (2) Double rounding */
return scm_i_from_double (scm_i_big2dbl (x) / SCM_REAL_VALUE (y));
(1) scm_integer_to_double_z (2) Double rounding */
return scm_i_from_double (scm_integer_to_double_z (scm_bignum (x))
/ SCM_REAL_VALUE (y));
else if (SCM_COMPLEXP (y))
{
a = scm_i_big2dbl (x);
goto complex_div;
}
return complex_div (scm_integer_to_double_z (scm_bignum (x)), y);
else if (SCM_FRACTIONP (y))
return scm_i_make_ratio (scm_product (x, SCM_FRACTION_DENOMINATOR (y)),
SCM_FRACTION_NUMERATOR (y));
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARGn, s_divide);
abort (); /* Unreachable. */
}
else if (SCM_REALP (x))
{
double rx = SCM_REAL_VALUE (x);
if (SCM_I_INUMP (y))
{
scm_t_inum yy = SCM_I_INUM (y);
if (yy == 0)
scm_num_overflow (s_divide);
else
/* FIXME: Precision may be lost here due to:
(1) The cast from 'scm_t_inum' to 'double'
(2) Double rounding */
return scm_i_from_double (rx / (double) yy);
}
return scm_i_from_double (rx / (double) SCM_I_INUM (y));
else if (SCM_BIGP (y))
{
/* FIXME: Precision may be lost here due to:
(1) The conversion from bignum to double
(2) Double rounding */
double dby = mpz_get_d (SCM_I_BIG_MPZ (y));
scm_remember_upto_here_1 (y);
return scm_i_from_double (rx / dby);
}
return scm_i_from_double (rx / scm_integer_to_double_z (scm_bignum (y)));
else if (SCM_REALP (y))
return scm_i_from_double (rx / SCM_REAL_VALUE (y));
else if (SCM_COMPLEXP (y))
{
a = rx;
goto complex_div;
}
return complex_div (rx, y);
else if (SCM_FRACTIONP (y))
return scm_i_from_double (rx / scm_i_fraction2double (y));
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARGn, s_divide);
abort () ; /* Unreachable. */
}
else if (SCM_COMPLEXP (x))
{
double rx = SCM_COMPLEX_REAL (x);
double ix = SCM_COMPLEX_IMAG (x);
if (SCM_I_INUMP (y))
{
scm_t_inum yy = SCM_I_INUM (y);
if (yy == 0)
scm_num_overflow (s_divide);
else
{
/* FIXME: Precision may be lost here due to:
(1) The conversion from 'scm_t_inum' to double
(2) Double rounding */
double d = yy;
double d = SCM_I_INUM (y);
return scm_c_make_rectangular (rx / d, ix / d);
}
}
else if (SCM_BIGP (y))
{
/* FIXME: Precision may be lost here due to:
(1) The conversion from bignum to double
(2) Double rounding */
double dby = mpz_get_d (SCM_I_BIG_MPZ (y));
scm_remember_upto_here_1 (y);
return scm_c_make_rectangular (rx / dby, ix / dby);
double d = scm_integer_to_double_z (scm_bignum (y));
return scm_c_make_rectangular (rx / d, ix / d);
}
else if (SCM_REALP (y))
{
double yy = SCM_REAL_VALUE (y);
return scm_c_make_rectangular (rx / yy, ix / yy);
double d = SCM_REAL_VALUE (y);
return scm_c_make_rectangular (rx / d, ix / d);
}
else if (SCM_COMPLEXP (y))
{
@ -5838,13 +5742,15 @@ scm_divide (SCM x, SCM y)
{
double t = ry / iy;
double d = iy * (1.0 + t * t);
return scm_c_make_rectangular ((rx * t + ix) / d, (ix * t - rx) / d);
return scm_c_make_rectangular ((rx * t + ix) / d,
(ix * t - rx) / d);
}
else
{
double t = iy / ry;
double d = ry * (1.0 + t * t);
return scm_c_make_rectangular ((rx + ix * t) / d, (ix - rx * t) / d);
return scm_c_make_rectangular ((rx + ix * t) / d,
(ix - rx * t) / d);
}
}
else if (SCM_FRACTIONP (y))
@ -5852,28 +5758,17 @@ scm_divide (SCM x, SCM y)
/* FIXME: Precision may be lost here due to:
(1) The conversion from fraction to double
(2) Double rounding */
double yy = scm_i_fraction2double (y);
return scm_c_make_rectangular (rx / yy, ix / yy);
double d = scm_i_fraction2double (y);
return scm_c_make_rectangular (rx / d, ix / d);
}
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARGn, s_divide);
abort (); /* Unreachable. */
}
else if (SCM_FRACTIONP (x))
{
if (SCM_I_INUMP (y))
{
scm_t_inum yy = SCM_I_INUM (y);
if (yy == 0)
scm_num_overflow (s_divide);
else
if (scm_is_exact_integer (y))
return scm_i_make_ratio (SCM_FRACTION_NUMERATOR (x),
scm_product (SCM_FRACTION_DENOMINATOR (x), y));
}
else if (SCM_BIGP (y))
{
return scm_i_make_ratio (SCM_FRACTION_NUMERATOR (x),
scm_product (SCM_FRACTION_DENOMINATOR (x), y));
}
else if (SCM_REALP (y))
/* FIXME: Precision may be lost here due to:
(1) The conversion from fraction to double
@ -5881,24 +5776,61 @@ scm_divide (SCM x, SCM y)
return scm_i_from_double (scm_i_fraction2double (x) /
SCM_REAL_VALUE (y));
else if (SCM_COMPLEXP (y))
{
/* FIXME: Precision may be lost here due to:
(1) The conversion from fraction to double
(2) Double rounding */
a = scm_i_fraction2double (x);
goto complex_div;
}
return complex_div (scm_i_fraction2double (x), y);
else if (SCM_FRACTIONP (y))
return scm_i_make_ratio (scm_product (SCM_FRACTION_NUMERATOR (x), SCM_FRACTION_DENOMINATOR (y)),
scm_product (SCM_FRACTION_NUMERATOR (y), SCM_FRACTION_DENOMINATOR (x)));
return scm_i_make_ratio (scm_product (SCM_FRACTION_NUMERATOR (x),
SCM_FRACTION_DENOMINATOR (y)),
scm_product (SCM_FRACTION_NUMERATOR (y),
SCM_FRACTION_DENOMINATOR (x)));
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARGn, s_divide);
abort (); /* Unreachable. */
}
else
return scm_wta_dispatch_2 (g_divide, x, y, SCM_ARG1, s_divide);
abort (); /* Unreachable. */
}
SCM_PRIMITIVE_GENERIC (scm_i_divide, "/", 0, 2, 1,
(SCM x, SCM y, SCM rest),
"Divide the first argument by the product of the remaining\n"
"arguments. If called with one argument @var{z1}, 1/@var{z1} is\n"
"returned.")
#define FUNC_NAME s_scm_i_divide
{
while (!scm_is_null (rest))
{ x = scm_divide (x, y);
y = scm_car (rest);
rest = scm_cdr (rest);
}
return scm_divide (x, y);
}
#undef FUNC_NAME
SCM
scm_divide (SCM x, SCM y)
{
if (SCM_UNBNDP (y))
{
if (SCM_UNBNDP (x))
return scm_wta_dispatch_0 (g_scm_i_divide, s_scm_i_divide);
if (SCM_NUMBERP (x))
return invert (x);
else
return scm_wta_dispatch_1 (g_scm_i_divide, x, SCM_ARG1,
s_scm_i_divide);
}
if (!SCM_NUMBERP (x))
return scm_wta_dispatch_2 (g_scm_i_divide, x, y, SCM_ARG1,
s_scm_i_divide);
if (!SCM_NUMBERP (y))
return scm_wta_dispatch_2 (g_scm_i_divide, x, y, SCM_ARG2,
s_scm_i_divide);
return divide (x, y);
}
double
scm_c_truncate (double x)