On 8/12/2015 9:07 AM, D Wyatt wrote:
so I 'get' that -5**2 = -25 and (-5)**2 is 25, BUT if you write a function
def sq(x):
""" Output: sq returns the square of its input
input x: a number (int or float)
"""
return x**2
and pass it a negative number it handles it as though the argument is
in parentheses.
I find this confusing. Can someone explain?
the passed in number is a single object. But when parsing a line,
"-5**2", exponentiation happens first, then negation of the result. The
parens around the -5 force evaluation as a number.
Consider this:
def sq1(x):
sgn = int(x<0)
return sgn*abs(x)**2
That's effectively what the parser does.
Emile
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