On 05/24/2012 09:23 PM, SherjilOzair wrote:
> def adder():
> s = 0
> def a(x):
> s += x
> return sum
> return a
>
> pos, neg = adder(), adder()
> for i in range(10):
> print pos(i), neg(-2*i)
>
> This should work, right? Why does it not?
>
Guess that depends on what you mean by work. First, it gets a syntax
error on the print function call, because you omitted the parens. When
I fixed that, I got
UnboundLocalError: local variable 's' referenced before assignment
so I fixed that, and got
inconsistent use of tabs and spaces in indentation
because you mistakenly used tabs for indentation. Then I got the output
<built-in function sum> <built-in function sum>
because sum is a built-in function. Presumably you meant to return s,
not sum.
Here's what I end up with, and it seems to work fine in Python 3.2 on Linux:
def adder():
s = 0
def a(x):
nonlocal s
s += x
return s
return a
pos, neg = adder(), adder()
for i in range(10):
print (pos(i), neg(-2*i))
.....
Output is:
0 0
1 -2
3 -6
6 -12
10 -20
15 -30
21 -42
28 -56
36 -72
45 -90
--
DaveA
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