## Following True or False?

on 27 Aug 2012

### Walter Roberson (view profile)

Consider the following example. a and b are two random variables. The loop will exit if and only if a+b=1. Is it true or false?

```      a=rand;
b=rand;
while(a+b == 1)
a=rand;
b=rand;
end```

#### 1 Comment

on 27 Aug 2012

I found that sometimes the sum was exceeding 1 or less than 1. Why?

## Products

### Walter Roberson (view profile)

on 27 Aug 2012

While executes as long as the given condition is true, so the loop would only execute as long as the sum was 1.

Note: please take time to review the following: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

on 27 Aug 2012

How can I overcome this problem? How to satisfy that condition? It should be a +b = 1. No other values should come.

Jan Simon

### Jan Simon (view profile)

on 27 Aug 2012

If a+b must be 1, simply use:

```a = rand;  b = 1 - a;
```

It is extremely unlikely that two random numbers will have a sum of 1. I think the probability is in the magnitude of 10^-53. Therefore rejecting the values until the sum equals 1 will take a looong time.

Walter Roberson

### Walter Roberson (view profile)

on 27 Aug 2012
```      a=rand;
b=rand;
while(a+b ~= 1)
a=rand;
b=rand;
end```

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