Modifying code for creating random numbers

[Objective Zero]

Hey,

I found the following method on the web but I do not want all these decimals places. I only want things like 5.2 or 7.4 etc...

How would I adjust this method to do that?

-(float)randomFloatBetween:(float)num1 andLargerFloat:(float)num2
{
    int startVal = num1*10000;
    int endVal = num2*10000; 

    int randomValue = startVal + (arc4random() % (endVal - startVal));
    float a = randomValue;

    return (a / 10000.0);
}

[Duncan C]

Originally Posted by Objective Zero

Hey,

I found the following method on the web but I do not want all these decimals places. I only want things like 5.2 or 7.4 etc...

How would I adjust this method to do that?

-(float)randomFloatBetween:(float)num1 andLargerFloat:(float)num2
{
    int startVal = num1*10000;
    int endVal = num2*10000; 

    int randomValue = startVal + (arc4random() % (endVal - startVal));
    float a = randomValue;

    return (a / 10000.0);
}

Because of the way computers represent floating point numbers in binary, a decimal number doesn't really have "a number of decimal places." The number is stored internally as a sum of fractions of powers of 2.

0.1, for example, is roughly 1/16+1/32+1/256+1/512+1/4096 (plus some even smaller fractions.)

If you use code like this

float num = 1.1
NSLog(@"num = %.9f", num);

You will get something like

"num = 1.099999999997"

If you want to display a number to a smaller number of decimal places, use string formatting to do it. Like:

NSString* numString = [NSString stringWithFormat:@"%.1f", num];

That will give you a string like 5.2 or 7.4 as you want.

[Objective Zero]

Hmm, maybe I have another issue at hand here. So I guess my real issue here is that I don't really care about the # of decimal places. Its just that, I just want arc4random to pick up the the tenth in the decimal places. So I only want it to choose things like 1.5,1.6,1.7. I do not want it picking numbers like 1.567, 1.832.

[rocotilos]

Originally Posted by Objective Zero

Hmm, maybe I have another issue at hand here. So I guess my real issue here is that I don't really care about the # of decimal places. Its just that, I just want arc4random to pick up the the tenth in the decimal places. So I only want it to choose things like 1.5,1.6,1.7. I do not want it picking numbers like 1.567, 1.832.

Actually Duncan already gave u the answer. I'll modify it further in case you don't get it.

float num = [self randomFloatBetween:5.4 andLargerFloat:10.6];
NSString* numString = [NSString stringWithFormat:@"%.1f", num];

this will give u 5.6, 5.8 etc, but in NSString format. You cannot have exactly 5.6 in number/float because a float is a number that floats. you give it a value of 5.6, it will actually hold 5.600000000231, or 5.5999999213.

Hope that helps.