Computer Science Canada

Rand.Int
Author:  AK.E [ Wed Jan 24, 2007 1:41 pm ]
Post subject:  Rand.Int
In my program I've been trying to get one variable to generate a number any from 2-14 and 28-36.

Turing:
var randomNumber : int := 0
|
| % some code goes here
|
loop
randomNumber := Rand.Int (2. 14)
end loop


I also want the variable to generate anything from 28 - 36.
Is there a way to do this? I don't want any numbers from 15 - 27.
If there is more information that you need just ask.
Author:  Teti [ Wed Jan 24, 2007 1:53 pm ]
Post subject:  Re: Rand.Int
Its hard to help without more code to see how it will work with your program.
Author:  ericfourfour [ Wed Jan 24, 2007 2:10 pm ]
Post subject:  RE:Rand.Int
You can try getting a random number between 2 and 22. If it is greater than 14, add 14. I'm sure there is a formula you can use as well.
Author:  agnivohneb [ Wed Jan 24, 2007 2:33 pm ]
Post subject:  Re: Rand.Int
You can try something like this
code:
var randomNumber : int := 0
    |
    | % some code goes here
    |
loop
    randomNumber := Rand.Int (2, 36)
    exit when randomNumber <= 14 or randomNumber >= 28
end loop

I have a question for you how did you get it to say turing then write the code in the turing colors
Author:  [Gandalf] [ Wed Jan 24, 2007 5:15 pm ]
Post subject:  Re: Rand.Int
Or you could use two Rand.Int() calls, which would be slightly more efficient then the above while loop. Not a big deal though.

agnivohneb, use [syntax="Turing"]code goes here[/syntax].
Author:  Cervantes [ Wed Jan 24, 2007 5:17 pm ]
Post subject:  RE:Rand.Int
Use syntax tags. [ syntax="turing"] code [ /syntax]


agnivohneb's method would work, but it's a bad way to do it. On a bad day, it could take a long time to generate a random number between 2 and 36 that is <= 14 or >= 28. It's possible we could just keep drawing numbers between 15 and 27 for a long time.

ericfourfour's method, however, is good. We have to generate exactly one random number every time. No more.
Author:  Cervantes [ Wed Jan 24, 2007 5:26 pm ]
Post subject:  Re: Rand.Int
Gandalf @ Wed Jan 24, 2007 5:15 pm wrote:
Or you could use two Rand.Int() calls, which would be slightly more efficient then the above while loop. Not a big deal though.


2-14 has 13 possible values in the range, but 28-36 has 9 possible values. Thus, if you did something like this:
code:

if Rand.Int (0, 1) = 0 then
    put Rand.Int (2, 14)
else
    put Rand.Int (28, 36)
end if

The chances of getting a 28 is higher than the chances of getting a 2. You'd have to do correction for that by changing the Rand.Int (0,1) at the start to be more like Rand.Int (1, 13+9) then checking whether that is <= 13 or not. So, yeah: that's needlessly complicated. ericfourfour's method.

edit: [Gandalf], your name breaks the quote system. It's the use of [ and ].

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