SF bug 115831 and Ping's SF patch 101751, 0.0**-2.0 returns inf rather than

raise ValueError.  Checked in the patch as far as it went, but also changed
all of ints, longs and floats to raise ZeroDivisionError instead when raising
0 to a negative number.  This is what 754-inspired stds require, as the "true
result" is an infinity obtained from finite operands, i.e. it's a singularity.
Also changed float pow to not be so timid about using its square-and-multiply
algorithm.  Note that what math.pow does is unrelated to what builtin pow
does, and will still vary by platform.
This commit is contained in:
Tim Peters 2000-10-06 00:36:09 +00:00
parent 4779a0a6fd
commit c54d19043a
4 changed files with 102 additions and 62 deletions

View File

@ -2,44 +2,69 @@ import sys
import test_support
def powtest(type):
if (type!=float):
if type != float:
print " Testing 2-argument pow() function..."
for i in range(-1000, 1000):
if (pow(type(i),0)!=1):
if pow(type(i), 0) != 1:
raise ValueError, 'pow('+str(i)+',0) != 1'
if (pow(type(i),1)!=type(i)):
if pow(type(i), 1) != type(i):
raise ValueError, 'pow('+str(i)+',1) != '+str(i)
if (pow(type(0),1)!=type(0)):
if pow(type(0), 1) != type(0):
raise ValueError, 'pow(0,'+str(i)+') != 0'
if (pow(type(1),1)!=type(1)):
if pow(type(1), 1) != type(1):
raise ValueError, 'pow(1,'+str(i)+') != 1'
for i in range(-100, 100):
if (pow(type(i),3)!=i*i*i):
if pow(type(i), 3) != i*i*i:
raise ValueError, 'pow('+str(i)+',3) != '+str(i*i*i)
pow2=1
pow2 = 1
for i in range(0,31):
if (pow(2,i)!=pow2):
if pow(2, i) != pow2:
raise ValueError, 'pow(2,'+str(i)+') != '+str(pow2)
if (i!=30): pow2=pow2*2
if i != 30 : pow2 = pow2*2
for othertype in int, long:
for i in range(-10, 0) + range(1, 10):
ii = type(i)
for j in range(1, 11):
jj = -othertype(j)
try:
pow(ii, jj)
except ValueError:
pass # taking an int to a neg int power should fail
else:
raise ValueError, "pow(%s, %s) did not fail" % (ii, jj)
for othertype in int, long, float:
for i in range(1, 100):
zero = type(0)
exp = -othertype(i/10.0)
if exp == 0:
continue
try:
pow(zero, exp)
except ZeroDivisionError:
pass # taking zero to any negative exponent should fail
else:
raise ValueError, "pow(%s, %s) did not fail" % (zero, exp)
print " Testing 3-argument pow() function..."
il, ih = -20, 20
jl, jh = -5, 5
kl, kh = -10, 10
compare = cmp
if (type==float):
il=1
if type == float:
il = 1
compare = test_support.fcmp
elif (type==int):
jl=0
elif (type==long):
jl,jh = 0, 15
elif type == int:
jl = 0
elif type == long:
jl, jh = 0, 15
for i in range(il, ih+1):
for j in range(jl,jh+1):
for j in range(jl, jh+1):
for k in range(kl, kh+1):
if (k!=0):
if k != 0:
if compare(pow(type(i),j,k), pow(type(i),j)% type(k)):
raise ValueError, "pow(" +str(i)+ "," +str(j)+ \
"," +str(k)+ ") != pow(" +str(i)+ "," + \
@ -81,15 +106,15 @@ print
for i in range(-10, 11):
for j in range(0, 6):
for k in range(-7, 11):
if (j>=0 and k!=0):
o=pow(i,j) % k
n=pow(i,j,k)
if (o!=n): print 'Integer mismatch:', i,j,k
if (j>=0 and k<>0):
o=pow(long(i),j) % k
n=pow(long(i),j,k)
if (o!=n): print 'Long mismatch:', i,j,k
if (i>=0 and k<>0):
o=pow(float(i),j) % k
n=pow(float(i),j,k)
if (o!=n): print 'Float mismatch:', i,j,k
if j >= 0 and k != 0:
o = pow(i,j) % k
n = pow(i,j,k)
if o != n: print 'Integer mismatch:', i,j,k
if j >= 0 and k <> 0:
o = pow(long(i),j) % k
n = pow(long(i),j,k)
if o != n: print 'Long mismatch:', i,j,k
if i >= 0 and k <> 0:
o = pow(float(i),j) % k
n = pow(float(i),j,k)
if o != n: print 'Float mismatch:', i,j,k

View File

@ -449,20 +449,33 @@ float_pow(PyFloatObject *v, PyObject *w, PyFloatObject *z)
iv = v->ob_fval;
iw = ((PyFloatObject *)w)->ob_fval;
intw = (long)iw;
if (iw == intw && -10000 < intw && intw < 10000) {
/* Sort out special cases here instead of relying on pow() */
if (intw == 0) { /* x**0 is 1, even 0**0 */
PyFPE_START_PROTECT("pow", return 0)
if ((PyObject *)z!=Py_None) {
ix=fmod(1.0, z->ob_fval);
if (ix!=0 && z->ob_fval<0) ix+=z->ob_fval;
}
else ix=1.0;
PyFPE_END_PROTECT(ix)
return PyFloat_FromDouble(ix);
/* Sort out special cases here instead of relying on pow() */
if (iw == 0) { /* x**0 is 1, even 0**0 */
PyFPE_START_PROTECT("pow", return NULL)
if ((PyObject *)z != Py_None) {
ix = fmod(1.0, z->ob_fval);
if (ix != 0 && z->ob_fval < 0)
ix += z->ob_fval;
}
else
ix = 1.0;
PyFPE_END_PROTECT(ix)
return PyFloat_FromDouble(ix);
}
if (iv == 0.0) {
if (iw < 0.0) {
PyErr_SetString(PyExc_ZeroDivisionError,
"0.0 to a negative power");
return NULL;
}
return PyFloat_FromDouble(0.0);
}
if (iw == intw && intw > LONG_MIN) {
/* ruled out LONG_MIN because -LONG_MIN isn't representable */
errno = 0;
PyFPE_START_PROTECT("pow", return 0)
PyFPE_START_PROTECT("pow", return NULL)
if (intw > 0)
ix = powu(iv, intw);
else
@ -471,21 +484,13 @@ float_pow(PyFloatObject *v, PyObject *w, PyFloatObject *z)
}
else {
/* Sort out special cases here instead of relying on pow() */
if (iv == 0.0) {
if (iw < 0.0) {
PyErr_SetString(PyExc_ValueError,
"0.0 to a negative power");
return NULL;
}
return PyFloat_FromDouble(0.0);
}
if (iv < 0.0) {
PyErr_SetString(PyExc_ValueError,
"negative number to a float power");
return NULL;
}
errno = 0;
PyFPE_START_PROTECT("pow", return 0)
PyFPE_START_PROTECT("pow", return NULL)
ix = pow(iv, iw);
PyFPE_END_PROTECT(ix)
}
@ -495,13 +500,15 @@ float_pow(PyFloatObject *v, PyObject *w, PyFloatObject *z)
PyErr_SetFromErrno(PyExc_OverflowError);
return NULL;
}
if ((PyObject *)z!=Py_None) {
PyFPE_START_PROTECT("pow", return 0)
ix=fmod(ix, z->ob_fval); /* XXX To Be Rewritten */
if ( ix!=0 &&
((iv<0 && z->ob_fval>0) || (iv>0 && z->ob_fval<0) )) {
ix+=z->ob_fval;
}
if ((PyObject *)z != Py_None) {
PyFPE_START_PROTECT("pow", return NULL)
ix = fmod(ix, z->ob_fval); /* XXX To Be Rewritten */
if (ix != 0 &&
((iv < 0 && z->ob_fval > 0) ||
(iv > 0 && z->ob_fval < 0)
)) {
ix += z->ob_fval;
}
PyFPE_END_PROTECT(ix)
}
return PyFloat_FromDouble(ix);

View File

@ -483,8 +483,12 @@ int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
iv = v->ob_ival;
iw = w->ob_ival;
if (iw < 0) {
PyErr_SetString(PyExc_ValueError,
"integer to the negative power");
if (iv)
PyErr_SetString(PyExc_ValueError,
"integer to a negative power");
else
PyErr_SetString(PyExc_ZeroDivisionError,
"0 to a negative power");
return NULL;
}
if ((PyObject *)z != Py_None) {

View File

@ -1244,8 +1244,12 @@ long_pow(PyLongObject *a, PyLongObject *b, PyLongObject *c)
size_b = b->ob_size;
if (size_b < 0) {
PyErr_SetString(PyExc_ValueError,
"long integer to the negative power");
if (a->ob_size)
PyErr_SetString(PyExc_ValueError,
"long integer to a negative power");
else
PyErr_SetString(PyExc_ZeroDivisionError,
"zero to a negative power");
return NULL;
}
z = (PyLongObject *)PyLong_FromLong(1L);