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Re: Adding numbers larger than 2^31 - 1

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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
26 Oct 2011 07:27 PM
I'm messing around with some conjectures, and since Roblox throws a tantrum when you have numbers larger than 2,147,483,647, I made something that adds strings. So you can add like 20395832095820469832 and 2092385906824096 and get a real answer. I just made this in like five minutes, but it seems pretty useful.

function Add(a, b)
a, b = string.reverse(a), string.reverse(b)
local A, B = {}, {}
for x = 1, #a do
table.insert(A, tonumber(a:sub(x,x)))
end
for y = 1, #b do
table.insert(B, tonumber(b:sub(y,y)))
end
local numA = #A
for i = 1, #B do
A[i] = (A[i] or 0) + B[i]
end
local ok = false
repeat
ok = true
for i = 1, #A do
if A[i] > 9 then
ok = false
A[i+1] = (A[i+1] or 0) + 1
A[i] = A[i] - 10
end
end
until ok
return string.reverse(table.concat(A))
end

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ArceusInator is not online. ArceusInator
Joined: 10 Oct 2009
Total Posts: 30553
26 Oct 2011 07:28 PM
y u so math
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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
26 Oct 2011 07:29 PM
bcuz 44562665878976437622437848976653870388884783662598425855963436955852489526638748888307835667984873422673467987856626544 is not a Lychrel number.
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LocalChum is not online. LocalChum
Joined: 04 Mar 2011
Total Posts: 6906
26 Oct 2011 07:29 PM
y u so math
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crazypotato4 is not online. crazypotato4
Joined: 22 Feb 2010
Total Posts: 20000
26 Oct 2011 07:31 PM
arent lua numbers all 64 bit doubles

so they can hold liek 10^306 or something

right?

:l
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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
26 Oct 2011 07:35 PM
this can make numbers even BIGGER than that.
but, problem
10 + 01 = 10
false. :(
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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
26 Oct 2011 07:39 PM
nvm
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pwnedu46 is not online. pwnedu46
Joined: 23 May 2009
Total Posts: 7534
26 Oct 2011 08:00 PM
*tracks thread*

imma make one to subtract, multiply, and divide ^_^
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popinman322 is not online. popinman322
Joined: 04 Mar 2009
Total Posts: 5184
26 Oct 2011 08:01 PM
subtract == make one negative

Tack on the negative thang.

~+[CROOKITY BANDED SNAKES]+~
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pwnedu46 is not online. pwnedu46
Joined: 23 May 2009
Total Posts: 7534
26 Oct 2011 08:10 PM
@Popin: I thought that was obvious. :3


function Subtract(a, b)
a, b = string.reverse(a), string.reverse(b)
local A, B = {}, {}
for x = 1, #a do
table.insert(A, tonumber(a:sub(x,x)))
end
for y = 1, #b do
table.insert(B, tonumber(b:sub(y,y)))
end
local numA = #A
for i = 1, #B do
A[i] = (A[i] or 0) - B[i]
end
local ok = false
repeat
ok = true
for i = 1, #A do
if A[i] > 9 then
ok = false
A[i+1] = (A[i+1] or 0) + 1
A[i] = A[i] - 10
end
end
until ok
return string.reverse(table.concat(A))
end


----------


print(Subtract(9999,1))
> 9998
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pwnedu46 is not online. pwnedu46
Joined: 23 May 2009
Total Posts: 7534
26 Oct 2011 08:12 PM
@Popin: I found it easier to simply change

    A[i] = (A[i] or 0) + B[i]

to

    A[i] = (A[i] or 0) - B[i]

 

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JulienDethurens is not online. JulienDethurens
Joined: 11 Jun 2009
Total Posts: 11046
26 Oct 2011 08:15 PM
Here's the easy way to subtract:

function Subtract(a, b)
return add(a, -b)
end
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Merlin11188 is not online. Merlin11188
Joined: 20 Dec 2007
Total Posts: 4158
26 Oct 2011 08:37 PM
OMG! I've been debating whether to make this or not because most languages suck when it comes to handling numerical data. Of course, this wastes more memory...
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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
26 Oct 2011 08:38 PM
*cough* assembly *cough*
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GoldenUrg is not online. GoldenUrg
Joined: 23 Aug 2009
Total Posts: 6428
26 Oct 2011 09:29 PM
I don't see why Lua would complain about numbers larger than "max int". Maybe you're trying to put it into an int property?

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popinman322 is not online. popinman322
Joined: 04 Mar 2009
Total Posts: 5184
27 Oct 2011 05:20 AM
@Golden

Numbers higher than the maximum are automatically set to the maximum.

This is the reason that Julien's code wouldn't work.

~+[CROOKITY BANDED SNAKES]+~
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popinman322 is not online. popinman322
Joined: 04 Mar 2009
Total Posts: 5184
27 Oct 2011 05:20 AM
the reason why*

~+[CROOKITY BANDED SNAKES]+~
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Radioaktiivinen is not online. Radioaktiivinen
Joined: 25 Apr 2009
Total Posts: 18629
27 Oct 2011 07:05 AM
the roblox 64 bit doubles cant hold a number of size 2^9001, they hold a number something like... lets say 2^51 because that sounds close, and then they scale it so its close to what you want but it still cant hold accurate numbers up to 2^9001
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booing is not online. booing
Joined: 04 May 2009
Total Posts: 6594
27 Oct 2011 10:19 AM
long int a;
i win
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arundel is not online. arundel
Joined: 21 Apr 2008
Total Posts: 5762
27 Oct 2011 10:42 AM
Only equal to or above 2^1024 will be the limit... which is quiet big still. But I get the number into a string concept for VERY large numbers.
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1waffle1 is not online. 1waffle1
Joined: 16 Oct 2007
Total Posts: 16381
27 Oct 2011 11:20 AM
Okay, look at it like this. If you do...

1429685792379857293857923587298375985734967592387
+
9732876529835789678943798273598749683746

You get 1.42968579e49.

Notice how it's missing FORTY DIGITS? It just rounded the entire equation to the ninth digit. Now the number is even SMALLER.
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pwnedu46 is not online. pwnedu46
Joined: 23 May 2009
Total Posts: 7534
27 Oct 2011 03:19 PM
"long int a; "

No, I win...
long long ago; // in a galaxy far, far away.
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pwnedu46 is not online. pwnedu46
Joined: 23 May 2009
Total Posts: 7534
27 Oct 2011 03:29 PM
"Of course, this wastes more memory..."

We're talking about a maximum difference of few KB, depending on the program. Any decent computer today has >= 2GB RAM. Because of that, you don't have to worry about memory management. If you use that in a program that even comes close to threatening to exceed the amount of RAM, you should have already been doing garbage collection.

The execution time to do basic mathematical operations will be (slightly) greater, but it's not a significant (or even noticeable) difference between execution times.
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HotThoth is not online. HotThoth
Forum Moderator
Joined: 24 Aug 2010
Total Posts: 1176
27 Oct 2011 05:50 PM
As for that example, wafflez-- you gotta remember that the version that it *prints* isn't necessarily as accurate as what it actually has stored in memory. So if it prints 1.42968579e49, it may still be storing more digits, but just (for the sake of people who don't want to read ~40 more digits) not printing them. You should try adding 9732876529835789678943798273598749683746 tons of times and see if the number eventually goes up.
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LocalChum is not online. LocalChum
Joined: 04 Mar 2011
Total Posts: 6906
27 Oct 2011 05:51 PM
Warm thoth above
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