4
Challenge: Implement incrementation without addition, multiplication, exponentiation, and any higher binary operators (and their opposites) in Python. Winner is the person who can do it in the least amount of code. You score 5 characters less if you can do it for negative numbers and without unary operators.
David Hewett
Posted 2013-07-26T23:14:08.100
Reputation: 57
16
-~i
Just good ol' unary - and bitwise-NOT.
Demo
>>> i = 3
>>> -~i
4
>>> i = 0
>>> -~i
1
>>> i = -3
>>> -~i
-2
arshajii
Posted 2013-07-26T23:14:08.100
Reputation: 2 142
10
I'm not a python guy, so here we go:
len(' '*i+' ')
According to the docs, I don't use addition, only string concatenation and repetition.
Johannes Kuhn
Posted 2013-07-26T23:14:08.100
Reputation: 7 122
1
Not shortest, but another way. This time no maths or binary operators involved at all. But it only works on numbers greater than -1.
len(range(-1,x))
Proof:
>>> inc = lambda x: len(range(-1,x))
>>> inc(7)
8
>>> inc(100)
101
Definitely out of contention but this does it for all positive and negative integers, again no math, no unary tricks.
len(range(-1,x)) or range(x,1)[1]
Proof:
>>> inc = lambda x:len(range(-1,x)) or range(x,1)[1]
>>> for i in range(-2,2): print i, inc(i)
...
-2 -1
-1 0
0 1
1 2
-1 on 33-5: len(range(-1,x))or range(x,1)[1]. The score is 27=32-5 then. – Erik the Outgolfer – 2016-07-14T16:22:33.373
0
sum((i,1))
Demo
>>> i = -3
>>> sum((i,1))
-2
>>> i = 0
>>> sum((i,1))
1
>>> i = 3
>>> sum((i,1))
4
arshajii
Posted 2013-07-26T23:14:08.100
Reputation: 2 142
isnt this pretty much addition? – David Hewett – 2013-07-27T19:55:01.740
@DavidHewett At it's core, it is addition. But this does not explicitly use +. The challenge description as-is seems to permit this; correct me if I'm wrong. – arshajii – 2013-07-27T20:24:12.597
the description states addition, and a sum of two numbers is the same thing as addition. – David Hewett – 2013-07-28T07:44:41.957
@DavidHewett So we can't use any function that, somewhere in its C implementation, uses addition? Also note that sum returns the sum of an iterable, in this case the tuple (i,1). – arshajii – 2013-07-28T12:24:42.733
You can use a function that uses addition, but not a function that "does" addition, if that makes any sense. – David Hewett – 2013-07-28T19:20:30.993
3There's no clear distinction between a function that uses addition and one that does addition. E.g., sum() can also be used to concatenate tuples: sum([(2,3), (4,5)], ()) returns (2, 3, 4, 5). – flornquake – 2013-07-28T20:15:05.257
@DavidHewett It's impossible to differentiate the two. – arshajii – 2013-07-28T22:05:12.840
0
27-5=22
It's not really very short, but it doesn't use len(), range(), sum() and other stuff which definitely has a lot of increments and additions in it. Works with negative numbers, and no unary operations. Only pure, natural, raw, organic bitwise magic :)
j=i
k=1
while i<=j:i^=k;k<<=1
Demo:
>>> def inc(i):
... j=i
... k=1
... while i<=i:i^=k;k<<=1
... return i
...
>>> inc(1)
2
>>> inc(2)
3
>>> inc(20)
21
>>> inc(-24)
-23
>>>
(UPD: Sorry, I'm not sure whether newlines are counted as chars, if yes, it should be 29 not 27...)
Ivan Anishchuk
Posted 2013-07-26T23:14:08.100
Reputation: 111
yeah nevermind, i figured it out. im not 100% perfect with python, so i wouldnt think of using string concatenation. pretty good! – David Hewett – 2013-07-26T23:46:16.167
2Writing a good code golf challenge is hard. It is part of the [tag:code-golf] game to stretch the rules to the limit if it makes your scoring better. – Johannes Kuhn – 2013-07-26T23:48:19.333