random number between 2 numbers

Hello,

I m looking at the game 2048.
I think I will try to make this one but then in smalltalk.

At the beginning you have a 4 x 4 grid where 2 of the boxes have the
number 2.
Now I wonder how can I take care the the 2 boxes which contains the
number 2 are random choosen.

I know Visualworks has a Random Class but I do not see how I can make it
work so a number between 1 and 16 is choosen two times.

Also later on the game I have to make it work that random numbers are
added but they have to be a number which is a power of 2.

How can I solve both cases ?

Roelof

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Hi Roelof!

On 10.04.2014 08:09, Roelof Wobben wrote:
> I know Visualworks has a Random Class but I do not see how I can make it
> work so a number between 1 and 16 is choosen two times.

As with most programming languages, a random number generator usually returns a value in a specific range. Depending on the concrete subclass of Random, the range of the returned value varies. Most of them return floating point values in the range [0..1). So if you want to get numbers from the range [1..16] you need to scale and shift it like
  number := ((random * 16) + 1) truncated.

> Also later on the game I have to make it work that random numbers are
> added but they have to be a number which is a power of 2.

If all numbers need to be powers of two, you can use a random number generator to create the exponent, just scale the exponent to your needs.

And a side note: Since the implementations are not truly random, your should use them as expected: Reuse a initialized Random object, do not create a new object for every #next call.

Regards
  Jan
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Jan Weerts schreef op 10-4-2014 11:24:
Hmm, that can be a problem.  As long as the games runs a new object is
added with a number which must be a power of 2.

You can see the game running here : http://gabrielecirulli.github.io/2048/

Roelof

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| rnd |
Transcript clear.
rnd := Random new.
2048 timesRepeat: [ |randomNumber|
	randomNumber := (rnd next * 15) rounded + 1. " 1-> 16 included "
	Transcript tab; show: randomNumber]. 

Sorry but i do not work.
When I copie this in a workspace I see a Message not understood ; astring.

Roelof


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Jan Weerts schreef op 11-4-2014 10:24:
> Hi Roelof!
>
> The problem is, that randomNumber is not a string but a number and #show: expects a string.
> You should be able to see the problem in the debugger. This is a very, very, very (did i mention "very") powerful tool in the smalltalk ide. Some people even develop only using the debugger and i myself find me often tweaking a method multiple times in the debugger until it works as expected.
>
>

Thanks,

You are right except this time I did not fully understand the error message.

Roelof

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Roelof Wobben schreef op 11-4-2014 13:27:
Another question:

Is there info how I can take care that I make a new set based on the
contents of numbers.
So lets say that numbers contains 2 and 5. I want to make a new set
which contains a 2 at position 2 and position 5.
I tried this numbers do: [cijfer | grid at: cijfer put: 2 ] but that is
not working.

Roelof

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On 4/11/2014 10:10 AM, Roelof Wobben wrote:
> Roelof Wobben schreef op 11-4-2014 13:27:

Roelof,

You generally do not want or need to concern yourself about where in a
set things go.  Try this:

| grid |

grid := Set new.

numbers do: [:cijfer | grid add: cijfer ].

or, if numbers is an OrderedCollection, you can do:

| grid |

grid := Set new.

grid addAll: numbers.

hth,


--
Donald [|]

Joel Cairo: "You always have a very smooth explanation."
Sam Spade: "What do you want me to do? Learn to stutter?"
- The Maltese Falcon

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