Write a function that returns something different every time it is called

Question

All these functional languages that return the same value every time a function is called give me a headache.

Your task is to write a function that returns something different every time it is called.

Here are the rules:

• Your function must continue to return something different every time it is run

• It must return a different value on your computer than it does on my computer

• Your function must be guaranteed to be different (no random numbers)

• +20 if your code gets time from the system or an online clock

Answer 1

Perl (7 bytes)

sub{$$}

Well, until processes IDs run out, this should return something else each time it's being called.

Alternatively, if you think this is not fine, because it will return the same value for the same instance of program, there is an alternate version which only works in newer versions of Perl which automatically increases process ID every time it's being called. It's 9 bytes long, however.

sub{$$++}

Answer 2

T-SQL, 13

PRINT NEWID()

Relatively uninspiring challenge, but it's rare that you can show off an instance of true brevity in SQL.

Answer 3

Perl, 67 (but growing slowly) char

open X,"+<$0";seek X,66,0;print$y=<DATA>,%ENV;print X++$y
__END__
0

Output the environment of the current machine, plus a hard coded number that is updated in the source code each time you run the script.

Answer 4

Python, 28

def f(x=[f]):x+=[1];return x

Since python has mutable default arguments x will be different every time you call f. The starting element gives you a memory address, which changes each time you define the function. Example output:

>>> def f(x=[]): x+=[1]; return x
... 
>>> f()
[<function f at 0x1047527d0>, 1]
>>> f()
[<function f at 0x1047527d0>, 1, 1]
>>> f()
[<function f at 0x1047527d0>, 1, 1, 1]

Answer 5

DOS - 27 chars

echo "X" >> random.txt
dir

Not only will your byte size be different, even if you put it in an empty directory your volume serial number won't match mine.

Answer 6

Haskell - 95

import Data.Time.Clock.POSIX
import System.IO.Unsafe
f _=fromEnum$unsafePerformIO getPOSIXTime

Example:

> f 0
-7269056719496922816
> f 0
-7269056004375922816
> f 0
-7269055316663922816

Answer 7

C [46 bytes]

#include<stdio.h>
main(int*x){printf("%x",&x);}

Theoretically this may return the same address but practically the probability is rather low.

Answer 8

Bash, 18, obvious

head /dev/urandom

Answer 9

Python, 56

import uuid
import time
print uuid.getnode(),time.time()

Answer 10

J, 11 bytes - True function

In J, printing the date is merely: 6!:0 '' but the question asks for a function (not absolutely sure other solutions follow this requirement), which gives the idea of the following 11-characters function: (6!:0@])&'' which outputs each time something different whatever its argument is (note that function with no-argument should be accepted, but answers with statements for printing the time shouldn't).

Answer 11

C++, 38 chars

int *r(){int*s;int n=0;s=&n;return s;}

Run int main(){std::cout<<r();} with the above, and it is guaranteed to return a different address every time.

Answer 12

bash+curl - 24 chars +20

curl -s time.nist.gov:13

Answer 13

Python 52

A different version of what @Hovercouch suggested:

def f(x=[f]):x+=[__import__("time").time()];return x


>>> f()
[<function f at 0x049F1A30>, 1394652231.0]
>>> f()
[<function f at 0x049F1A30>, 1394652231.0, 1394652232.746]
>>> f()
[<function f at 0x049F1A30>, 1394652231.0, 1394652232.746, 1394652423.971]
>>> f()
[<function f at 0x049F1A30>, 1394652231.0, 1394652232.746, 1394652423.971, 1394652428.137]

Although the odds of getting different output on all computers is not zero!