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New restriction on pow(x, y, z): If z is not None, x and y must be of

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integer types, and y must be >= 0.  See discussion at
http://sf.net/tracker/index.php?func=detail&aid=457066&group_id=5470&atid=105470
This commit is contained in:
Tim Peters 2001-09-03 08:35:41 +00:00
parent 5d2b77cf31
commit 32f453eaa4
9 changed files with 79 additions and 49 deletions
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10
Doc/lib/libfuncs.tex
View file

@ -519,8 +519,14 @@ the interpreter.
case, all arguments are converted to float and a float result is
delivered. For example, \code{10**2} returns \code{100}, but
\code{10**-2} returns \code{0.01}. (This last feature was added in
Python 2.2. In Python 2.1 and before, a negative second argument
would raise an exception.)
Python 2.2. In Python 2.1 and before, if both arguments were of integer
types and the second argument was negative, an exception was raised.)
If the second argument is negative, the third argument must be omitted.
If \var{z} is present, \var{x} and \var{y} must be of integer types,
and \var{y} must be non-negative. (This restriction was added in
Python 2.2. In Python 2.1 and before, floating 3-argument \code{pow()}
returned platform-dependent results depending on floating-point
rounding accidents.)
\end{funcdesc}
\begin{funcdesc}{range}{\optional{start,} stop\optional{, step}}

4
Lib/test/output/test_pow
View file

@ -22,8 +22,4 @@ The number in both columns should match.
-3L -3L
-7L -7L
3.0 3.0
-5.0 -5.0
-1.0 -1.0
-7.0 -7.0

23
Lib/test/test_b2.py
View file

@ -82,15 +82,26 @@
if fcmp(pow(2.,20), 1024.*1024.): raise TestFailed, 'pow(2.,20)'
if fcmp(pow(2.,30), 1024.*1024.*1024.): raise TestFailed, 'pow(2.,30)'
#
# XXX These don't work -- negative float to the float power...
#if fcmp(pow(-2.,0), 1.): raise TestFailed, 'pow(-2.,0)'
#if fcmp(pow(-2.,1), -2.): raise TestFailed, 'pow(-2.,1)'
#if fcmp(pow(-2.,2), 4.): raise TestFailed, 'pow(-2.,2)'
#if fcmp(pow(-2.,3), -8.): raise TestFailed, 'pow(-2.,3)'
#
if fcmp(pow(-2.,0), 1.): raise TestFailed, 'pow(-2.,0)'
if fcmp(pow(-2.,1), -2.): raise TestFailed, 'pow(-2.,1)'
if fcmp(pow(-2.,2), 4.): raise TestFailed, 'pow(-2.,2)'
if fcmp(pow(-2.,3), -8.): raise TestFailed, 'pow(-2.,3)'
from types import FloatType
for x in 2, 2L, 2.0:
for y in 10, 10L, 10.0:
for z in 1000, 1000L, 1000.0:
if isinstance(x, FloatType) or \
isinstance(y, FloatType) or \
isinstance(z, FloatType):
try:
pow(x, y, z)
except TypeError:
pass
else:
raise TestFailed("3-arg float pow() should have "
"raised TypeError %r" % (x, y, z))
else:
if fcmp(pow(x, y, z), 24.0):
raise TestFailed, 'pow(%s, %s, %s)' % (x, y, z)

9
Lib/test/test_long.py
View file

@ -315,9 +315,18 @@ def checkit(*args):
for z in special:
if z != 0 :
if y >= 0:
expected = pow(longx, longy, long(z))
got = pow(x, y, z)
checkit('pow', x, y, '%', z)
else:
try:
pow(longx, longy, long(z))
except TypeError:
pass
else:
raise TestFailed("pow%r should have raised "
"TypeError" % ((longx, longy, long(z))))
# ---------------------------------------------------------------- do it

18
Lib/test/test_pow.py
View file

@ -64,6 +64,15 @@ def powtest(type):
for j in range(jl, jh+1):
for k in range(kl, kh+1):
if k != 0:
if type == float or j < 0:
try:
pow(type(i),j,k)
except TypeError:
pass
else:
raise TestFailed("expected TypeError from "
"pow%r" % ((type(i), j, k)))
continue
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)+ "," + \
@ -96,10 +105,6 @@ def powtest(type):
print `pow(5L,2) % -8`, `pow(5L,2,-8)`
print
print pow(3.0,3.0) % 8, pow(3.0,3.0,8)
print pow(3.0,3.0) % -8, pow(3.0,3.0,-8)
print pow(3.0,2) % -2, pow(3.0,2,-2)
print pow(5.0,2) % -8, pow(5.0,2,-8)
print
for i in range(-10, 11):
@ -112,8 +117,3 @@ def powtest(type):
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

6
Misc/NEWS
View file

@ -3,6 +3,12 @@ What's New in Python 2.2a3?
Core
- The 3-argument builtin pow() no longer allows a third non-None argument
if either of the first two arguments is a float, or if both are of
integer types and the second argument is negative (in which latter case
the arguments are converted to float, so this is really the same
restriction).
- The builtin dir() now returns more information, and sometimes much
more, generally naming all attributes of an object, and all attributes
reachable from the object via its class, and from its class's base

22
Objects/floatobject.c
View file

@ -492,11 +492,13 @@ static PyObject *
float_pow(PyObject *v, PyObject *w, PyObject *z)
{
double iv, iw, ix;
/* XXX Doesn't handle overflows if z!=None yet; it may never do so :(
* The z parameter is really only going to be useful for integers and
* long integers. Maybe something clever with logarithms could be done.
* [AMK]
*/
if ((PyObject *)z != Py_None) {
PyErr_SetString(PyExc_TypeError,
"3rd argument to floating pow() must be None");
return NULL;
}
CONVERT_TO_DOUBLE(v, iv);
CONVERT_TO_DOUBLE(w, iw);
@ -538,16 +540,6 @@ float_pow(PyObject *v, PyObject *w, PyObject *z)
PyErr_SetFromErrno(PyExc_OverflowError);
return NULL;
}
if ((PyObject *)z != Py_None) {
double iz;
CONVERT_TO_DOUBLE(z, iz);
PyFPE_START_PROTECT("pow", return 0)
ix = fmod(ix, iz); /* XXX To Be Rewritten */
if (ix != 0 && ((iv < 0 && iz > 0) || (iv > 0 && iz < 0) )) {
ix += iz;
}
PyFPE_END_PROTECT(ix)
}
return PyFloat_FromDouble(ix);
}

5
Objects/intobject.c
View file

@ -575,6 +575,11 @@ int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
CONVERT_TO_LONG(v, iv);
CONVERT_TO_LONG(w, iw);
if (iw < 0) {
if ((PyObject *)z != Py_None) {
PyErr_SetString(PyExc_TypeError, "integer pow() arg "
"3 must not be specified when arg 2 is < 0");
return NULL;
}
/* Return a float. This works because we know that
this calls float_pow() which converts its
arguments to double. */

11
Objects/longobject.c
View file

@ -1598,12 +1598,17 @@ long_pow(PyObject *v, PyObject *w, PyObject *x)
size_b = b->ob_size;
if (size_b < 0) {
/* Return a float. This works because we know that
this calls float_pow() which converts its
arguments to double. */
Py_DECREF(a);
Py_DECREF(b);
Py_DECREF(c);
if (x != Py_None) {
PyErr_SetString(PyExc_TypeError, "integer pow() arg "
"3 must not be specified when arg 2 is < 0");
return NULL;
}
/* Return a float. This works because we know that
this calls float_pow() which converts its
arguments to double. */
return PyFloat_Type.tp_as_number->nb_power(v, w, x);
}
z = (PyLongObject *)PyLong_FromLong(1L);