Question abour rand()

ruby-talk
1

Dear Sirs,

I'm looking for a way to create a random sequence of numbers using the 'rand' method. I can think of something like:

···

-----
while pipi == TRUE
  if x > 1950 || x < 2000
     return x
     pipi = FALSE
------

Since however the book that I'm reading has not introduced while/else/if etc. I'm thinking that there must be an easier and probably more sensible way to approach this. As far as I've read rand(2000) will give random numbers from 0-to-2000 no matter what.

NOTE: I don't want to use another method just to do the job.

thanks in advance & best regards

Panagiotis (atmosx) Atmatzidis

email: atma@convalesco.org
URL: http://www.convalesco.org
GnuPG ID: 0xFC4E8BB4
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4
--
The wise man said: "Never argue with an idiot. They bring you down to their level and beat you with experience."

2

Hello,

I'm looking for a way to create a random sequence of numbers using the 'rand' method. I can think of something like:

-----
while pipi == TRUE
if x > 1950 || x < 2000

Perhaps you were thinking of "and" rather than "or" because all number
is either greater than 1950 or smaller than 2000.

Since however the book that I'm reading has not introduced while/else/if etc. I'm thinking that there must be an easier and probably more sensible way to approach this. As far as I've read rand(2000) will give random numbers from 0-to-2000 no matter what.

Does 'rand(50) + 1950' do what you want ?

Cheers,

···

--
JJ Fleck
PCSI1 Lycée Kléber

3

Hmm. Looks as though you want the range 1951..1999. Well, that's easy
enough:

  rand(49) + 1951

(Note that rand(49) returns anything from 0 to 48, inclusive.)

-s

···

On 2009-12-29, Panagiotis Atmatzidis <atma@convalesco.org> wrote:

while pipi == TRUE
  if x > 1950 || x < 2000
     return x
     pipi = FALSE

--
Copyright 2009, all wrongs reversed. Peter Seebach / usenet-nospam@seebs.net
| Seebs.Net <-- lawsuits, religion, and funny pictures
Fair game (Scientology) - Wikipedia <-- get educated!

4

Panagiotis Atmatzidis wrote:

Dear Sirs,

I'm looking for a way to create a random sequence of numbers using the
'rand' method. I can think of something like:

-----
while pipi == TRUE
  if x > 1950 || x < 2000
     return x
     pipi = FALSE
------

Since however the book that I'm reading has not introduced while/else/if
etc. I'm thinking that there must be an easier and probably more
sensible way to approach this. As far as I've read rand(2000) will give
random numbers from 0-to-2000 no matter what

Use Seebs' suggestion.

NOTE: I don't want to use another method just to do the job.

Then you are probably being silly. It will make for more readable and
more reusable code if you encapsulate this in a method. Having lots of
short methods is generally a *good* thing.

thanks in advance & best regards

Panagiotis (atmosx) Atmatzidis

email: atma@convalesco.org
URL: http://www.convalesco.org
GnuPG ID: 0xFC4E8BB4
gpg --keyserver x-hkp://pgp.mit.edu --recv-keys 0xFC4E8BB4

Best,

···

--
Marnen Laibow-Koser
http://www.marnen.org
marnen@marnen.org
--
Posted via http://www.ruby-forum.com/\.

5

Hi,

I'm looking for a way to create a random sequence of numbers using the 'rand' method. I can think of something like:

-----
while pipi == TRUE
  if x > 1950 || x < 2000
     return x
     pipi = FALSE
------

Since however the book that I'm reading has not introduced while/else/if etc. I'm thinking that there must be an easier and probably more sensible way to approach this. As far as I've read rand(2000) will give random numbers from 0-to-2000 no matter what.

NOTE: I don't want to use another method just to do the job.

thanks in advance & best regards

The "rand" method has been mentioned. Here are just some
considerations about the above code.

You don't need a loop for calculating a random value. (There is a
random algorithm below.) But when use a loop, then you either say
"return" or leave it by a condition but not both.

  cond = true
  while cond do
    ...
    if some_condition then
      cond = false
    end
    ...
  end

_or_

  loop do
    ...
    break if some_condition
    ...
  end

Note that "break" can even return values:

  result = loop do
    break "hi"
  end
  result == "hi"

And here is an example of a very simple random implementation:

  class R
    def initialize
      @r = 0
    end
    def nextval
      @r = ((@r * 0xabcd) + 0x73737) % 0x1_0000_0000
      @r >> 16
    end
  end
  r = R.new
  new_random_value = r.iterate
  random_value_below_fifty = r.iterate % 50

Bertram

···

Am Dienstag, 29. Dez 2009, 18:51:53 +0900 schrieb Panagiotis Atmatzidis:

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
*
Discover String#notempty? at <http://raa.ruby-lang.org/project/step&gt;\.

6

Panagiotis Atmatzidis wrote:

I'm looking for a way to create a random sequence of numbers using the
'rand' method.

Others have answered the 'random number between 1950 and 2000' bit.

In terms of creating a "sequence" of these values, here are a couple of
options to consider.

(1) Build an array.

a =
10.times { a << rand(50) }

This array (a) is an object which can be returned, passed to other
functions etc. The above code hard-codes the number of values to build
(10), but you could choose this dynamically at run-time instead.

(2) Yield the values.

For code which wants to "return" multiple values, you can instead
"yield" the values to a block which the caller provides. You can yield
multiple times, thus calling the block multiple times. In other
programming languages you might call this a "callback function"

def generate_random(n=10)
  n.times do
    yield rand(50)
  end
end

generate_random do |r|
  puts "I got #{r}!"
end

Note that you can legitimately yield an infinite number of times,
because the block can abort the sequence when it wants. So in the
following example, the user of the function decides when they don't want
any more random numbers:

def generate_infinite
  loop do
    yield rand(50)
  end
end

count = 0
generate_infinite do |r|
  puts "I got #{r}!"
  count += 1
  break unless count < 10
end

A more advanced way to do this is with an 'Enumerator' object, but I'd
say you should start with the above for now.

···

--
Posted via http://www.ruby-forum.com/\.

7

"Walk before you run."

···

On 29.12.2009 18:00, Marnen Laibow-Koser wrote:

NOTE: I don't want to use another method just to do the job.

Then you are probably being silly. It will make for more readable and
more reusable code if you encapsulate this in a method. Having lots of
short methods is generally a *good* thing.

--
Phillip Gawlowski