cpython/Objects/complexobject.c

/* Complex object implementation */

/* Borrows heavily from floatobject.c */

/* Submitted by Jim Hugunin */

#ifndef WITHOUT_COMPLEX

#include "Python.h"

/* Precisions used by repr() and str(), respectively.

   The repr() precision (17 significant decimal digits) is the minimal number
   that is guaranteed to have enough precision so that if the number is read
   back in the exact same binary value is recreated.  This is true for IEEE
   floating point by design, and also happens to work for all other modern
   hardware.

   The str() precision is chosen so that in most cases, the rounding noise
   created by various operations is suppressed, while giving plenty of
   precision for practical use.
*/

#define PREC_REPR	17
#define PREC_STR	12

/* elementary operations on complex numbers */

static Py_complex c_1 = {1., 0.};

Py_complex
c_sum(Py_complex a, Py_complex b)
{
	Py_complex r;
	r.real = a.real + b.real;
	r.imag = a.imag + b.imag;
	return r;
}

Py_complex
c_diff(Py_complex a, Py_complex b)
{
	Py_complex r;
	r.real = a.real - b.real;
	r.imag = a.imag - b.imag;
	return r;
}

Py_complex
c_neg(Py_complex a)
{
	Py_complex r;
	r.real = -a.real;
	r.imag = -a.imag;
	return r;
}

Py_complex
c_prod(Py_complex a, Py_complex b)
{
	Py_complex r;
	r.real = a.real*b.real - a.imag*b.imag;
	r.imag = a.real*b.imag + a.imag*b.real;
	return r;
}

Py_complex
c_quot(Py_complex a, Py_complex b)
{
	/******************************************************************
	This was the original algorithm.  It's grossly prone to spurious
	overflow and underflow errors.  It also merrily divides by 0 despite
	checking for that(!).  The code still serves a doc purpose here, as
	the algorithm following is a simple by-cases transformation of this
	one:

	Py_complex r;
	double d = b.real*b.real + b.imag*b.imag;
	if (d == 0.)
		errno = EDOM;
	r.real = (a.real*b.real + a.imag*b.imag)/d;
	r.imag = (a.imag*b.real - a.real*b.imag)/d;
	return r;
	******************************************************************/

	/* This algorithm is better, and is pretty obvious:  first divide the
	 * numerators and denominator by whichever of {b.real, b.imag} has
	 * larger magnitude.  The earliest reference I found was to CACM
	 * Algorithm 116 (Complex Division, Robert L. Smith, Stanford
	 * University).  As usual, though, we're still ignoring all IEEE
	 * endcases.
	 */
	 Py_complex r;	/* the result */
 	 const double abs_breal = b.real < 0 ? -b.real : b.real;
	 const double abs_bimag = b.imag < 0 ? -b.imag : b.imag;

	 if (abs_breal >= abs_bimag) {
 		/* divide tops and bottom by b.real */
	 	if (abs_breal == 0.0) {
	 		errno = EDOM;
	 		r.real = r.imag = 0.0;
	 	}
	 	else {
	 		const double ratio = b.imag / b.real;
	 		const double denom = b.real + b.imag * ratio;
	 		r.real = (a.real + a.imag * ratio) / denom;
	 		r.imag = (a.imag - a.real * ratio) / denom;
	 	}
	}
	else {
		/* divide tops and bottom by b.imag */
		const double ratio = b.real / b.imag;
		const double denom = b.real * ratio + b.imag;
		assert(b.imag != 0.0);
		r.real = (a.real * ratio + a.imag) / denom;
		r.imag = (a.imag * ratio - a.real) / denom;
	}
	return r;
}

Py_complex
c_pow(Py_complex a, Py_complex b)
{
	Py_complex r;
	double vabs,len,at,phase;
	if (b.real == 0. && b.imag == 0.) {
		r.real = 1.;
		r.imag = 0.;
	}
	else if (a.real == 0. && a.imag == 0.) {
		if (b.imag != 0. || b.real < 0.)
			errno = ERANGE;
		r.real = 0.;
		r.imag = 0.;
	}
	else {
		vabs = hypot(a.real,a.imag);
		len = pow(vabs,b.real);
		at = atan2(a.imag, a.real);
		phase = at*b.real;
		if (b.imag != 0.0) {
			len /= exp(at*b.imag);
			phase += b.imag*log(vabs);
		}
		r.real = len*cos(phase);
		r.imag = len*sin(phase);
	}
	return r;
}

static Py_complex
c_powu(Py_complex x, long n)
{
	Py_complex r, p;
	long mask = 1;
	r = c_1;
	p = x;
	while (mask > 0 && n >= mask) {
		if (n & mask)
			r = c_prod(r,p);
		mask <<= 1;
		p = c_prod(p,p);
	}
	return r;
}

static Py_complex
c_powi(Py_complex x, long n)
{
	Py_complex cn;

	if (n > 100 || n < -100) {
		cn.real = (double) n;
		cn.imag = 0.;
		return c_pow(x,cn);
	}
	else if (n > 0)
		return c_powu(x,n);
	else
		return c_quot(c_1,c_powu(x,-n));

}

PyObject *
PyComplex_FromCComplex(Py_complex cval)
{
	register PyComplexObject *op;

	/* PyObject_New is inlined */
	op = (PyComplexObject *) PyObject_MALLOC(sizeof(PyComplexObject));
	if (op == NULL)
		return PyErr_NoMemory();
	PyObject_INIT(op, &PyComplex_Type);
	op->cval = cval;
	return (PyObject *) op;
}

PyObject *
PyComplex_FromDoubles(double real, double imag)
{
	Py_complex c;
	c.real = real;
	c.imag = imag;
	return PyComplex_FromCComplex(c);
}

double
PyComplex_RealAsDouble(PyObject *op)
{
	if (PyComplex_Check(op)) {
		return ((PyComplexObject *)op)->cval.real;
	}
	else {
		return PyFloat_AsDouble(op);
	}
}

double
PyComplex_ImagAsDouble(PyObject *op)
{
	if (PyComplex_Check(op)) {
		return ((PyComplexObject *)op)->cval.imag;
	}
	else {
		return 0.0;
	}
}

Py_complex
PyComplex_AsCComplex(PyObject *op)
{
	Py_complex cv;
	if (PyComplex_Check(op)) {
		return ((PyComplexObject *)op)->cval;
	}
	else {
		cv.real = PyFloat_AsDouble(op);
		cv.imag = 0.;
		return cv;
	}
}

static void
complex_dealloc(PyObject *op)
{
	PyObject_DEL(op);
}


static void
complex_to_buf(char *buf, PyComplexObject *v, int precision)
{
	if (v->cval.real == 0.)
		sprintf(buf, "%.*gj", precision, v->cval.imag);
	else
		sprintf(buf, "(%.*g%+.*gj)", precision, v->cval.real,
					     precision, v->cval.imag);
}

static int
complex_print(PyComplexObject *v, FILE *fp, int flags)
{
	char buf[100];
	complex_to_buf(buf, v,
		       (flags & Py_PRINT_RAW) ? PREC_STR : PREC_REPR);
	fputs(buf, fp);
	return 0;
}

static PyObject *
complex_repr(PyComplexObject *v)
{
	char buf[100];
	complex_to_buf(buf, v, PREC_REPR);
	return PyString_FromString(buf);
}

static PyObject *
complex_str(PyComplexObject *v)
{
	char buf[100];
	complex_to_buf(buf, v, PREC_STR);
	return PyString_FromString(buf);
}

static long
complex_hash(PyComplexObject *v)
{
	long hashreal, hashimag, combined;
	hashreal = _Py_HashDouble(v->cval.real);
	if (hashreal == -1)
		return -1;
	hashimag = _Py_HashDouble(v->cval.imag);
	if (hashimag == -1)
		return -1;
	/* Note:  if the imaginary part is 0, hashimag is 0 now,
	 * so the following returns hashreal unchanged.  This is
	 * important because numbers of different types that
	 * compare equal must have the same hash value, so that
	 * hash(x + 0*j) must equal hash(x).
	 */
	combined = hashreal + 1000003 * hashimag;
	if (combined == -1)
		combined = -2;
	return combined;
}

static PyObject *
complex_add(PyComplexObject *v, PyComplexObject *w)
{
	Py_complex result;
	PyFPE_START_PROTECT("complex_add", return 0)
	result = c_sum(v->cval,w->cval);
	PyFPE_END_PROTECT(result)
	return PyComplex_FromCComplex(result);
}

static PyObject *
complex_sub(PyComplexObject *v, PyComplexObject *w)
{
	Py_complex result;
	PyFPE_START_PROTECT("complex_sub", return 0)
	result = c_diff(v->cval,w->cval);
	PyFPE_END_PROTECT(result)
	return PyComplex_FromCComplex(result);
}

static PyObject *
complex_mul(PyComplexObject *v, PyComplexObject *w)
{
	Py_complex result;
	PyFPE_START_PROTECT("complex_mul", return 0)
	result = c_prod(v->cval,w->cval);
	PyFPE_END_PROTECT(result)
	return PyComplex_FromCComplex(result);
}

static PyObject *
complex_div(PyComplexObject *v, PyComplexObject *w)
{
	Py_complex quot;
	PyFPE_START_PROTECT("complex_div", return 0)
	errno = 0;
	quot = c_quot(v->cval,w->cval);
	PyFPE_END_PROTECT(quot)
	if (errno == EDOM) {
		PyErr_SetString(PyExc_ZeroDivisionError, "complex division");
		return NULL;
	}
	return PyComplex_FromCComplex(quot);
}

static PyObject *
complex_remainder(PyComplexObject *v, PyComplexObject *w)
{
        Py_complex div, mod;
	errno = 0;
	div = c_quot(v->cval,w->cval); /* The raw divisor value. */
	if (errno == EDOM) {
		PyErr_SetString(PyExc_ZeroDivisionError, "complex remainder");
		return NULL;
	}
	div.real = floor(div.real); /* Use the floor of the real part. */
	div.imag = 0.0;
	mod = c_diff(v->cval, c_prod(w->cval, div));

	return PyComplex_FromCComplex(mod);
}


static PyObject *
complex_divmod(PyComplexObject *v, PyComplexObject *w)
{
        Py_complex div, mod;
	PyObject *d, *m, *z;
	errno = 0;
	div = c_quot(v->cval,w->cval); /* The raw divisor value. */
	if (errno == EDOM) {
		PyErr_SetString(PyExc_ZeroDivisionError, "complex divmod()");
		return NULL;
	}
	div.real = floor(div.real); /* Use the floor of the real part. */
	div.imag = 0.0;
	mod = c_diff(v->cval, c_prod(w->cval, div));
	d = PyComplex_FromCComplex(div);
	m = PyComplex_FromCComplex(mod);
	z = Py_BuildValue("(OO)", d, m);
	Py_XDECREF(d);
	Py_XDECREF(m);
	return z;
}

static PyObject *
complex_pow(PyComplexObject *v, PyObject *w, PyComplexObject *z)
{
	Py_complex p;
	Py_complex exponent;
	long int_exponent;

 	if ((PyObject *)z!=Py_None) {
		PyErr_SetString(PyExc_ValueError, "complex modulo");
		return NULL;
	}
	PyFPE_START_PROTECT("complex_pow", return 0)
	errno = 0;
	exponent = ((PyComplexObject*)w)->cval;
	int_exponent = (long)exponent.real;
	if (exponent.imag == 0. && exponent.real == int_exponent)
		p = c_powi(v->cval,int_exponent);
	else
		p = c_pow(v->cval,exponent);

	PyFPE_END_PROTECT(p)
	if (errno == ERANGE) {
		PyErr_SetString(PyExc_ValueError,
				"0.0 to a negative or complex power");
		return NULL;
	}
	return PyComplex_FromCComplex(p);
}

static PyObject *
complex_neg(PyComplexObject *v)
{
	Py_complex neg;
	neg.real = -v->cval.real;
	neg.imag = -v->cval.imag;
	return PyComplex_FromCComplex(neg);
}

static PyObject *
complex_pos(PyComplexObject *v)
{
	Py_INCREF(v);
	return (PyObject *)v;
}

static PyObject *
complex_abs(PyComplexObject *v)
{
	double result;
	PyFPE_START_PROTECT("complex_abs", return 0)
	result = hypot(v->cval.real,v->cval.imag);
	PyFPE_END_PROTECT(result)
	return PyFloat_FromDouble(result);
}

static int
complex_nonzero(PyComplexObject *v)
{
	return v->cval.real != 0.0 || v->cval.imag != 0.0;
}

static int
complex_coerce(PyObject **pv, PyObject **pw)
{
	Py_complex cval;
	cval.imag = 0.;
	if (PyInt_Check(*pw)) {
		cval.real = (double)PyInt_AsLong(*pw);
		*pw = PyComplex_FromCComplex(cval);
		Py_INCREF(*pv);
		return 0;
	}
	else if (PyLong_Check(*pw)) {
		cval.real = PyLong_AsDouble(*pw);
		*pw = PyComplex_FromCComplex(cval);
		Py_INCREF(*pv);
		return 0;
	}
	else if (PyFloat_Check(*pw)) {
		cval.real = PyFloat_AsDouble(*pw);
		*pw = PyComplex_FromCComplex(cval);
		Py_INCREF(*pv);
		return 0;
	}
	return 1; /* Can't do it */
}

static PyObject *
complex_richcompare(PyObject *v, PyObject *w, int op)
{
	int c;
	Py_complex i, j;
	PyObject *res;

	if (op != Py_EQ && op != Py_NE) {
		PyErr_SetString(PyExc_TypeError,
			"cannot compare complex numbers using <, <=, >, >=");
		return NULL;
	}

	c = PyNumber_CoerceEx(&v, &w);
	if (c < 0)
		return NULL;
	if (c > 0) {
		Py_INCREF(Py_NotImplemented);
		return Py_NotImplemented;
	}
	if (!PyComplex_Check(v) || !PyComplex_Check(w)) {
		Py_DECREF(v);
		Py_DECREF(w);
		Py_INCREF(Py_NotImplemented);
		return Py_NotImplemented;
	}

	i = ((PyComplexObject *)v)->cval;
	j = ((PyComplexObject *)w)->cval;
	Py_DECREF(v);
	Py_DECREF(w);

	if ((i.real == j.real && i.imag == j.imag) == (op == Py_EQ))
		res = Py_True;
	else
		res = Py_False;

	Py_INCREF(res);
	return res;
}

static PyObject *
complex_int(PyObject *v)
{
	PyErr_SetString(PyExc_TypeError,
		   "can't convert complex to int; use e.g. int(abs(z))");
	return NULL;
}

static PyObject *
complex_long(PyObject *v)
{
	PyErr_SetString(PyExc_TypeError,
		   "can't convert complex to long; use e.g. long(abs(z))");
	return NULL;
}

static PyObject *
complex_float(PyObject *v)
{
	PyErr_SetString(PyExc_TypeError,
		   "can't convert complex to float; use e.g. abs(z)");
	return NULL;
}

static PyObject *
complex_conjugate(PyObject *self, PyObject *args)
{
	Py_complex c;
	if (!PyArg_ParseTuple(args, ":conjugate"))
		return NULL;
	c = ((PyComplexObject *)self)->cval;
	c.imag = -c.imag;
	return PyComplex_FromCComplex(c);
}

static PyMethodDef complex_methods[] = {
	{"conjugate",	complex_conjugate,	1},
	{NULL,		NULL}		/* sentinel */
};


static PyObject *
complex_getattr(PyComplexObject *self, char *name)
{
	if (strcmp(name, "real") == 0)
		return (PyObject *)PyFloat_FromDouble(self->cval.real);
	else if (strcmp(name, "imag") == 0)
		return (PyObject *)PyFloat_FromDouble(self->cval.imag);
	else if (strcmp(name, "__members__") == 0)
		return Py_BuildValue("[ss]", "imag", "real");
	return Py_FindMethod(complex_methods, (PyObject *)self, name);
}

static PyNumberMethods complex_as_number = {
	(binaryfunc)complex_add, 		/* nb_add */
	(binaryfunc)complex_sub, 		/* nb_subtract */
	(binaryfunc)complex_mul, 		/* nb_multiply */
	(binaryfunc)complex_div, 		/* nb_divide */
	(binaryfunc)complex_remainder,		/* nb_remainder */
	(binaryfunc)complex_divmod,		/* nb_divmod */
	(ternaryfunc)complex_pow,		/* nb_power */
	(unaryfunc)complex_neg,			/* nb_negative */
	(unaryfunc)complex_pos,			/* nb_positive */
	(unaryfunc)complex_abs,			/* nb_absolute */
	(inquiry)complex_nonzero,		/* nb_nonzero */
	0,					/* nb_invert */
	0,					/* nb_lshift */
	0,					/* nb_rshift */
	0,					/* nb_and */
	0,					/* nb_xor */
	0,					/* nb_or */
	(coercion)complex_coerce,		/* nb_coerce */
	(unaryfunc)complex_int,			/* nb_int */
	(unaryfunc)complex_long,		/* nb_long */
	(unaryfunc)complex_float,		/* nb_float */
	0,					/* nb_oct */
	0,					/* nb_hex */
};

PyTypeObject PyComplex_Type = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,
	"complex",
	sizeof(PyComplexObject),
	0,
	(destructor)complex_dealloc,		/* tp_dealloc */
	(printfunc)complex_print,		/* tp_print */
	(getattrfunc)complex_getattr,		/* tp_getattr */
	0,					/* tp_setattr */
	0,					/* tp_compare */
	(reprfunc)complex_repr,			/* tp_repr */
	&complex_as_number,    			/* tp_as_number */
	0,					/* tp_as_sequence */
	0,					/* tp_as_mapping */
	(hashfunc)complex_hash, 		/* tp_hash */
	0,					/* tp_call */
	(reprfunc)complex_str,			/* tp_str */
	0,					/* tp_getattro */
	0,					/* tp_setattro */
	0,					/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,			/* tp_flags */
	0,					/* tp_doc */
	0,					/* tp_traverse */
	0,					/* tp_clear */
	complex_richcompare,			/* tp_richcompare */
};

#endif