Hi all,

I wondered if there was a more compact method of generating things like
a random string, or a random list of numbers than I'm using now (using
ruby 1.9.0-1)

array = [] ; 100.times {array << rand}
string = "" ; 100.times {string << (rand(26) + 97).chr}

The temptation is to use

array = [rand] * 100
string = (rand(26) + 97).chr * 100

but that only draws one random number a 100 times.

Is there a bit of syntax that I missed?
--
Posted via http://www.ruby-forum.com/.

On May 26, 2008, at 10:45, Boris Schmid wrote:

> Hi all,
>
> I wondered if there was a more compact method of generating things =20
> like
> a random string, or a random list of numbers than I'm using now (using
> ruby 1.9.0-1)

Array(100) { rand }

The block is evaluated for each element.

--=20
Mikael H=F8ilund=

-------- Original-Nachricht --------
> Datum: Mon, 26 May 2008 17:45:57 +0900
> Von: Boris Schmid <boris@bagofsouls.com>
> An: ruby-talk@ruby-lang.org
> Betreff: briefest method of generating a list of random numbers?

> Hi all,
>
> I wondered if there was a more compact method of generating things like
> a random string, or a random list of numbers than I'm using now (using
> ruby 1.9.0-1)
>
> array = [] ; 100.times {array << rand}
> string = "" ; 100.times {string << (rand(26) + 97).chr}
>
> The temptation is to use
>
> array = [rand] * 100
> string = (rand(26) + 97).chr * 100
>
> but that only draws one random number a 100 times.
>
> Is there a bit of syntax that I missed?
> --
> Posted via http://www.ruby-forum.com/.

Hello Boris,

> string = (rand(26) + 97).chr * 100
>
> but that only draws one random number a 100 times.

That's not correct - it draws a random number once, turns it into
a letter and then repeats it 100 times -

you could also write, e.g.,

string='x'*100 .

But what's wrong with the first - it looks fairly compact to me:

string = "" ; 100.times { string << (rand(26) + 97).chr}

You could add a srand(); in the bracket to call different
strings every time, but that's less compact

Best regards,

Axel
--
Psssst! Schon vom neuen GMX MultiMessenger gehört?
Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger

> But what's wrong with the first - it looks fairly compact to me:
>
> string = "" ; 100.times { string << (rand(26) + 97).chr}
>

For strings I'll have to use the one above, but arrays now read a bit
more natural (to my eyes). The size doesn't matter that much, but it is
simpler to understand.

population = Array.new(POP_SIZE) {
function_that_generates_a_random_individual }

vs the old

population = [] ; POP_SIZE.times {population <<
function_that_generates_a_random_individual }

Thanks both of you!
--
Posted via http://www.ruby-forum.com/.

On May 26, 11:16 am, Mikael Høilund <mik...@hoilund.org> wrote:
> On May 26, 2008, at 10:45, Boris Schmid wrote:
>
> > Hi all,
>
> > I wondered if there was a more compact method of generating things
> > like
> > a random string, or a random list of numbers than I'm using now (using
> > ruby 1.9.0-1)
>
> Array(100) { rand }

Don't you mean

Array.new(100) { rand }

Array(arg) creates an array equal to 'arg' (if it responds to .to_ary)
or an array containing precisly 'arg' otherwise. It never yields.

There is also

(1..100).map { rand }

And for strings

(1..100).map { (rand(26)+97).chr }.join

Lars

Boris Schmid wrote:

>> string = "" ; 100.times { string << (rand(26) + 97).chr}
>>
>
> For strings I'll have to use the one above,

Duh. I can just use the Array.new, and append a .join at the end to get
the random string. And Axel, I'm generating quite a lot of arrays in my
small prog, and using this shorter way makes it indeed clearer . It is
definitly worth it.

Example:


filter = Array.new(WINDOW) { bucket = Array.new(AMINO) {|i| (97 +
i).chr} }

was

filter = []
WINDOW.times {bucket = [] ; AMINO.times {|i| bucket << (97 + i).chr}
; filter << bucket}
--
Posted via http://www.ruby-forum.com/.

2008/5/26 Boris Schmid <boris@bagofsouls.com>:
>
>> But what's wrong with the first - it looks fairly compact to me:
>>
>> string = "" ; 100.times { string << (rand(26) + 97).chr}
>>
>
> For strings I'll have to use the one above,

Note that String#<< understands ints as being character codes - so you
do not need the .chr:

irb(main):005:0> str = 100.to_enum(:times).inject("") {|s,| s << (?a +
rand(26))}
=> "uepizlkepyoxxfkefosxxptvcpdiuwyexecngmftnidlyfnhq gmtndbzthhykdjjiyayzwvhatovzbxzqkhclnxwbqbsoxpszwk n"
irb(main):006:0>

I believe in 1.9 you can as well do

str = 100.times.inject("") {|s,| s << (?a + rand(26))}

Kind regards

robert

--
use.inject do |as, often| as.you_can - without end

On Mon, May 26, 2008 at 11:34 AM, Boris Schmid <boris@bagofsouls.com> wrote:
>
>> But what's wrong with the first - it looks fairly compact to me:
>>
>> string = "" ; 100.times { string << (rand(26) + 97).chr}
>>
>
> For strings I'll have to use the one above, but arrays now read a bit
> more natural (to my eyes). The size doesn't matter that much, but it is
> simpler to understand.

You could also do

Array.new(100) { 97 + rand(26) }.pack("c*")

Peter