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Converting a negative number to a positive number.

Posted on 2004-05-02
9
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Last Modified: 2010-04-17
Hi All,
I need to convert a negative number to a positive number.
int i=0,j=0;
i--;
if( j == 100)
{
   //I need to change the -i number to a +i number
   //if i = -1050 I need to change it to i = +1050 by using
   //the value of i.
   //i will be a random number
}
if(j== 50)
{
   //I need to change i back to the negative number
   //by using the value of i.
}

In other words check the negative value and change it
to it's positive counter part and vice versa.

Is there a simple way to do this?

Thank you very much for your time,
AJ.
0
Comment
Question by:arnold100
  • 3
  • 2
  • 2
  • +2
9 Comments
 
LVL 7

Expert Comment

by:madwax
ID: 10971701
Hi arnold100,

Maybe I misunderstood you question but can't you just multiple the number by -1?

if(number < 0)
{
    number = number * -1;
}


and vice versa if you want to convert a postivie number to a negative...
//jan
0
 
LVL 4

Expert Comment

by:SimonTay
ID: 10972009
Sounds good to me, or you can use the ABS(i) function in most languages, so

i=ABS(i) will make it positive always.
0
 

Author Comment

by:arnold100
ID: 10972023
Hi madwax,
i--;

if(i==-1080)//-1080 will be a random - number
{                //so i needs to be converted from it's
                 //negative side to it's positive side
                 //using the value of  i
     i = i*-1;//I tried with no luck.
}

When i is -1080, i needs to be converted to +1080.
In other words no mather what the value of -i is, it needs
to be fliped to it's +i side. Same value just + instead of -.
Hope this helps.

Thanks,
AJ.

0
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LVL 7

Expert Comment

by:madwax
ID: 10972118
Hi again,

What programming language are you using? This will be nescessary to know if that below doesn't work...

i = i * (-1);

Good luck,
//madwax
0
 

Author Comment

by:arnold100
ID: 10972186
I am working in c++. I tried the abs(); function that SimonTay listed above and it works for negative to positive. Is there a function for positive to negative?

Thanks SimonTay and madwax,
Aj.
0
 
LVL 44

Expert Comment

by:Arthur_Wood
ID: 10973480
simply multiply the original value by -1

Negative become postive, Postive becomes negative

X = 12;
Y = -1 * X;  //Y = -12   now



X = -12;
Y = -1 * X;   // y = 12  now


Is that what you need?

AW
0
 
LVL 4

Expert Comment

by:PerryDK
ID: 10973616
to convert from positive to negative or from negative to positive simpy use the urnary - operator;

i = -i;

for(int i = -5; i < 5; i++)
{
  int opposite = -i;
  cout << opposite << endl;
}

OUTPUT:
5
4
3
2
1
0
-1
-2
-3
-4
0
 
LVL 4

Accepted Solution

by:
PerryDK earned 125 total points
ID: 10973628
int i=0,j=0;
i--;
if( j == 100)
{
   //I need to change the -i number to a +i number
   if( i == -1050)
       i = -i;  // i now equals 1050;
}
if(j== 50)
{
   //I need to change i back to the negative number
   j = -j;  //j now equals -50
}
0
 

Author Comment

by:arnold100
ID: 10973877
Hi PerryDK,
The urnary is the answer. I had tried it before with what I thought
was no luck, but I tried it again now and you are 100% right. I run my program with it and I find that the number is changing from
positive to negative and then back in a split second. I have a bug in my code some where and now I have to track it down and fix it. I except your answer.

Thank you very much,
AJ.
0

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