details: http://hg.sympy.org/sympy/rev/876257540928
changeset: 1831:876257540928
user: Fredrik Johansson <[EMAIL PROTECTED]>
date: Mon Oct 20 16:48:16 2008 +0200
description:
Fix substitution of 0 in evalf of powers
diffs (51 lines):
diff -r 9292ed4fdd71 -r 876257540928 sympy/core/evalf.py
--- a/sympy/core/evalf.py Sun Oct 19 22:24:48 2008 +0200
+++ b/sympy/core/evalf.py Mon Oct 20 16:48:16 2008 +0200
@@ -419,6 +419,9 @@
if case == 1: return None, z, None, target_prec
if case == 2: return mpf_neg(z), None, target_prec, None
if case == 3: return None, mpf_neg(z), None, target_prec
+ # Zero raised to an integer power
+ if not re:
+ return None, None, None, None
# General complex number to arbitrary integer power
re, im = libmpc.mpc_pow_int((re, im), p, prec)
# Assumes full accuracy in input
@@ -443,6 +446,10 @@
# This determines the working precision that must be used
prec += 10
yre, yim, yre_acc, yim_acc = evalf(exp, prec, options)
+ # Special cases: x**0
+ if not (yre or yim):
+ return fone, None, prec, None
+
ysize = fastlog(yre)
# Restart if too big
# XXX: prec + ysize might exceed maxprec
@@ -458,6 +465,9 @@
return mpf_exp(yre, target_prec), None, target_prec, None
xre, xim, xre_acc, yim_acc = evalf(base, prec+5, options)
+ # 0**y
+ if not (xre or xim):
+ return None, None, None, None
# (real ** complex) or (complex ** complex)
if yim:
diff -r 9292ed4fdd71 -r 876257540928 sympy/core/tests/test_evalf.py
--- a/sympy/core/tests/test_evalf.py Sun Oct 19 22:24:48 2008 +0200
+++ b/sympy/core/tests/test_evalf.py Mon Oct 20 16:48:16 2008 +0200
@@ -179,3 +179,13 @@
assert abs(complex(pi+E*I) - (3.1415926535897931+2.7182818284590451j)) <
1e-10
raises(ValueError, "float(pi+x)")
raises(ValueError, "complex(pi+x)")
+
+def test_evalf_power_subs_bugs():
+ assert (x**2).evalf(subs={x:0}) == 0
+ assert sqrt(x).evalf(subs={x:0}) == 0
+ assert (x**Rational(2,3)).evalf(subs={x:0}) == 0
+ assert (x**x).evalf(subs={x:0}) == 1
+ assert (3**x).evalf(subs={x:0}) == 1
+ assert exp(x).evalf(subs={x:0}) == 1
+ assert ((2+I)**x).evalf(subs={x:0}) == 1
+ assert (0**x).evalf(subs={x:0}) == 1
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