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.
diff --git a/Lib/test/test_pow.py b/Lib/test/test_pow.py
index 6e3dda7..22c1972 100644
--- a/Lib/test/test_pow.py
+++ b/Lib/test/test_pow.py
@@ -2,44 +2,69 @@
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 @@
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
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 17f70b2..d776147 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -449,20 +449,33 @@
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 @@
}
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 @@
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);
diff --git a/Objects/intobject.c b/Objects/intobject.c
index b88a05d..c9d1f6a 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -483,8 +483,12 @@
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) {
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 65dcaa0..bfb431f 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -1244,8 +1244,12 @@
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);