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"""
Module of functions that are like ufuncs in acting on arrays and optionally
storing results in an output array.
"""
__all__ = ['fix', 'isneginf', 'isposinf', 'sign', 'log2']
import numeric as nx
from numeric import asarray, empty, empty_like, isinf, signbit, zeros
import umath
def fix(x, y=None):
""" Round x to nearest integer towards zero.
"""
x = asarray(x)
if y is None:
y = nx.floor(x)
else:
nx.floor(x, y)
if x.ndim == 0:
if (x<0):
y += 1
else:
y[x<0] = y[x<0]+1
return y
def isposinf(x, y=None):
"""Return a boolean array y with y[i] True for x[i] = +Inf.
If y is an array, the result replaces the contents of y.
"""
if y is None:
y = empty(x.shape, dtype=nx.bool_)
umath.logical_and(isinf(x), ~signbit(x), y)
return y
def isneginf(x, y=None):
"""Return a boolean array y with y[i] True for x[i] = -Inf.
If y is an array, the result replaces the contents of y.
"""
if y is None:
y = empty(x.shape, dtype=nx.bool_)
umath.logical_and(isinf(x), signbit(x), y)
return y
def sign(x, y=None):
"""sign(x) gives an array with shape of x with elexents defined by sign
function: where x is less than 0 return -1, where x greater than 0, a=1,
elsewhere a=0.
"""
x = asarray(x)
if y is None:
y = zeros(x.shape, dtype=nx.int_)
if x.ndim == 0:
if x < 0:
y -= 1
elif x > 0:
y += 1
else:
y[x<0] = -1
y[x>0] = 1
return y
_log2 = umath.log(2)
def log2(x, y=None):
"""Returns the base 2 logarithm of x
If y is an array, the result replaces the contents of y.
"""
x = asarray(x)
if y is None:
y = umath.log(x)
else:
umath.log(x, y)
y /= _log2
return y
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