def _eval_power(b, e):
"""
b is Real but not equal to rationals, integers, 0.5, oo, -oo, nan
e is symbolic object but not equal to 0, 1
(-p) ** r -> exp(r * log(-p)) -> exp(r * (log(p) + I*Pi)) ->
-> p ** r * (sin(Pi*r) + cos(Pi*r) * I)
"""
if isinstance(e, Number):
if isinstance(e, Integer):
prec = b._prec
return Real._new(mlib.mpf_pow_int(b._mpf_, e.p, prec, rnd), prec)
e, prec = e._as_mpf_op(b._prec)
b = b._mpf_
try:
y = mpf_pow(b, e, prec, rnd)
return Real._new(y, prec)
except mlib.ComplexResult:
re, im = mlibc.mpc_pow((b, mlib.fzero), (e, mlib.fzero), prec, rnd)
return Real._new(re, prec) + Real._new(im, prec) * S.ImaginaryUnit
def _eval_power(b, e):
"""
b is Real but not equal to rationals, integers, 0.5, oo, -oo, nan
e is symbolic object but not equal to 0, 1
(-p) ** r -> exp(r * log(-p)) -> exp(r * (log(p) + I*Pi)) ->
-> p ** r * (sin(Pi*r) + cos(Pi*r) * I)
"""
if isinstance(e, Number):
if isinstance(e, Integer):
prec = b._prec
return Real._new(mlib.mpf_pow_int(b._mpf_, e.p, prec, rnd), prec)
e, prec = e._as_mpf_op(b._prec)
b = b._mpf_
try:
y = mpf_pow(b, e, prec, rnd)
return Real._new(y, prec)
except mlib.ComplexResult:
re, im = mlibc.mpc_pow((b, mlib.fzero), (e, mlib.fzero), prec, rnd)
return Real._new(re, prec) + Real._new(im, prec) * S.ImaginaryUnit
def evalf_pow(v, prec, options):
target_prec = prec
base, exp = v.args
# We handle x**n separately. This has two purposes: 1) it is much
# faster, because we avoid calling evalf on the exponent, and 2) it
# allows better handling of real/imaginary parts that are exactly zero
if exp.is_Integer:
p = exp.p
# Exact
if not p:
return fone, None, prec, None
# Exponentiation by p magnifies relative error by |p|, so the
# base must be evaluated with increased precision if p is large
prec += int(math.log(abs(p),2))
re, im, re_acc, im_acc = evalf(base, prec+5, options)
# Real to integer power
if re and not im:
return mpf_pow_int(re, p, target_prec), None, target_prec, None
# (x*I)**n = I**n * x**n
if im and not re:
z = fpowi(im, p, target_prec)
case = p % 4
if case == 0: return z, None, target_prec, None
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
return finalize_complex(re, im, target_prec)
# Pure square root
if exp is S.Half:
xre, xim, xre_acc, yim_acc = evalf(base, prec+5, options)
# General complex square root
if xim:
re, im = libmpc.mpc_sqrt((xre or fzero, xim), prec)
return finalize_complex(re, im, prec)
if not xre:
return None, None, None, None
# Square root of a negative real number
if mpf_lt(xre, fzero):
return None, mpf_sqrt(mpf_neg(xre), prec), None, prec
# Positive square root
return mpf_sqrt(xre, prec), None, prec, None
# We first evaluate the exponent to find its magnitude
# 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
if ysize > 5:
prec += ysize
yre, yim, yre_acc, yim_acc = evalf(exp, prec, options)
# Pure exponential function; no need to evalf the base
if base is S.Exp1:
if yim:
re, im = libmpc.mpc_exp((yre or fzero, yim), prec)
return finalize_complex(re, im, target_prec)
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:
re, im = libmpc.mpc_pow((xre or fzero, xim or fzero), (yre or fzero, yim),
target_prec)
return finalize_complex(re, im, target_prec)
# complex ** real
if xim:
re, im = libmpc.mpc_pow_mpf((xre or fzero, xim), yre, target_prec)
return finalize_complex(re, im, target_prec)
# negative ** real
elif mpf_lt(xre, fzero):
re, im = libmpc.mpc_pow_mpf((xre, fzero), yre, target_prec)
return finalize_complex(re, im, target_prec)
# positive ** real
else:
return mpf_pow(xre, yre, target_prec), None, target_prec, None
