Change a non-floating point number the largest step [closed]

Question

Declare a numeric variable that is not floating point and do an operation that changes the value with the largest amount of difference so the result of the variable is far from the original value.

Solutions will be scored based on the magnitude of the difference between initial value and the value after changed, and shortness of code.

Edit:
I realize that this was a bit vague - sorry about that, it's my first try on code golf...

I want to also emphasize that the result must not cause overflow. So once the variable is declared with a specific type (which must not be floating point), the result would have to be valid within that type.

Answer 1

D (15 chars 2^64-1 difference)

ulong o=0;o=~o;

uses unsigned long and logical NOT to get max value

note that using ucent would get me to 2^128-1 difference (if it were to be implemented at least)

Answer 2

Java (55 26 19 chars, Diff: 2^64-1 = 18446744073709551615)

Given a very unclear spec on what we're supposed to be doing, here's a best try :-) Obviously I will easily be beat out by languages that have arbitrary precision integers like Python or APL/J.

long o=Long.MIN_VALUE;o+=Long.MAX_VALUE+Long.MAX_VALUE;

Demo: http://www.ideone.com/7HyCW

EDIT: Shorter version, making use of Long underflow to wrap around from MIN_VALUE to MAX_VALUE (26 chars):

long o=Long.MIN_VALUE;o--;

Demo: http://www.ideone.com/Qfao7

EDIT 2: Shortest yet taking into account @ratchet freak's suggestions:

long o=1L<<63;o=~o;

Demo: http://www.ideone.com/2M9oa

Answer 3

Haskell - 8 characters (Infinite difference)

f=f.(+1)

Use f on Integer.

Answer 4

Golfscript

2{.?}9*

7 chars, unimaginably large difference. (The loop executes 9 times. The first time maps 2 -> 2^2 = 4. The second time maps 4 -> 4^4 = 256. The third time maps 256 -> 256^256 ~= 3.23 * 10^616. The fourth time overflows memory, but not the datatype...)

Answer 5

C with SSE2 (79 chars, Difference: 2^128-1 = 3.4e38)

#include<emmintrin.h>
main(){__m128i v=_mm_set1_epi8(-1);v=_mm_xor_si128(v,v);}

This initially sets the 128 bit unsigned int v to its maximum value, and then changes this value to 0 by XORing v with itself.

Answer 6

J - 16 characters

a=.<.<:(a=.2)^31

The value of a changes from 2 to 2147483647. The calculation makes the value become float, but the final result is integer.

There are also extended integers, but I don't know if they would be acceptable.

a=.(a=.0)+!100000x

Yes, that really spells out mathematically as !100000. J can crunch it (in a few minutes), brute force.

Answer 7

Python (13 chars, Difference: 9^(9^9) (369,693,100 digits!))

a=0;a=9**9**9

I believe that the result of this operation is not a float, isn't it?

If that's problem because it doesn't yield the result...

Mathematica (11 chars, Difference: only 15,151,335 digits)

If it's still a problem because this value is not the maximum possible, then, a=2^1073741696;a*=-1 (20 chars) will do the work.

Answer 8

bc 15chars:

On my system I can go until 8^8^8 without error, but 6^6^6 would already be too long to report it here, so take 5^5^5 as an example; 7^7^7 is in the range of one minute on a single core 2Ghz machine. With 8 you should have some time left.

echo "k=8^8^8;k*=-1;k" | bc 

printable result for one page:

echo "k=5^5^5;k*=-1;k" | bc 

-1911012597945477520356404559703964599198081048990094337139512789246\ 52053024261580301205938651973985026558644015579446223535921278867380\ 69722884101469159866020879618967571957018392816603380476112259755336\ 26101001482651123413147768252411493094447176965282756285196737514395\ 35754247909321920664188301178716912255242107005070906467438287085144\ 99502565861944615431835113798491336917799281274338404315492368555267\ 83596374102105331546031353725325748636909159778690328266459182983815\ 23028693657287369142264813129174376213632573032164528297948686257624\ 53622180176732249405676428193600787207138370723553054463561539464011\ 85348493792719514594505508232749221605848912910945189959948686199543\ 14766693801303717616359259447974616422005088507946980448713320513316\ 07391342305401988725700383298012460501970134673971759090273894939238\ 17315786996845899794781068042822436093783946335265422815704302832442\ 38551508231649096728571217170812323279048181726832751011274678231741\ 09858886837085220007117334922539133223007561471804290075276777933523\ 06200618286012455254243061006894805446584704820650982664319360960388\ 73625851074707434063628697657670269925864995355797631817390255089133\ 12232947439303439561613283340728316634982581452268620043077990846881\ 03804187368324800903873596212919633602583120781673673742533322879296\ 90720549059562140688882599124458184237959786347648431567376092362509\ 03715117989414242622702200662864868678687101829808728025606931019492\ 80830825044198424796792058908817112327192301455582916746795197430548\ 02640464685400273399386079859446596150175258696581144756851004156868\ 77309037124825353438392853975987494584970500382250124892840018265900\ 56251286187629938044407340142347062055785305325034918189589707199305\ 66218851296318750174353596028220103821161604854512103931331225633226\ 07664362366882968502088394961428304847391139916696226499485636852347\ 12873294796680884509405893951104650944137909502276545653133018670633\ 52132302846051943438139981056140065259530073179077271106578349417464\ 26847209561346473277485842382748996687550525043942182321913572230540\ 66715373374248543645663782045701654593218154053548393614250664498585\ 40330746646854189014813434771465031503795417577862281177658587694168\ 0908203125

Answer 9

BrainF***, 3 characters, theoretically unlimited difference

[+]

Some implementations of BF wrap. "True" BF allows for unlimited integers. This has a difference of whatever you want it to be, plus it's only 3 characters long :)