All of the replies say the same thing -- this is good.
My learning project for Ruby is implementing a turning grille cipher. I want to allocate a n*m matrix where n and m are read from stdin.
I have the n[] (the rows) array, no sweat. But the m part (the columns) is rather elusive.
Here's my latest code:
@m = Array.new(@rows)
@M = @m.each {|row| @m[row] = Array.new(@cols)}
It doesn't work, either... 
Try:
matrix = Array.new(@rows, Array.new(@cols))
-austin
– Austin Ziegler, austin@halostatue.ca on 2002.11.08 at 18.29.35
On Sat, 9 Nov 2002 08:18:31 +0900, Ted wrote:
All of the replies say the same thing – this is good. My learning
project for Ruby is implementing a turning grille cipher. I want
to allocate a n*m matrix where n and m are read from stdin.I have the n (the rows) array, no sweat. But the m part (the
columns) is rather elusive.Here’s my latest code:
@m = Array.new(@rows)
@M = @m.each {|row| @m[row] = Array.new(@cols)}
“Ted” ted@datacomm.com writes:
All of the replies say the same thing – this is good.
My learning project for Ruby is implementing a turning grille cipher. I want to allocate a n*m matrix where n and m are read from stdin.I have the n (the rows) array, no sweat. But the m part (the columns) is rather elusive.
Here’s my latest code:
@m = Array.new(@rows)
@M = @m.each {|row| #=> warning, ‘row’ is always nil here
@m[row] = #=> == @m[nil] which is invalid
Array.new(@cols)}
matrix=Array.new(@rows)
0.upto(@rows-1) {|i| matrix[i] = Array.new(@cols)}
YS.
Hi –
All of the replies say the same thing – this is good. My learning
project for Ruby is implementing a turning grille cipher. I want to
allocate a n*m matrix where n and m are read from stdin.I have the n (the rows) array, no sweat. But the m part (the
columns) is rather elusive.
There’s a Matrix class shipped with Ruby – have a look at
lib/matrix.rb.
Here’s my latest code:
@m = Array.new(@rows)
@M = @m.each {|row| @m[row] = Array.new(@cols)}It doesn’t work, either…
Don’t forget that #each returns the receiver. In other words, in
this:
a = [1,2,3].each {|x| x * 20}
a ends up as [1,2,3], not as [20,40,60]. The transformation is
thrown away.
In your example, you’re trying to save the transformation explicitly
to the array that’s being transformed… but let Ruby do it for you
For that purpose, you can use #map. In fact, you can just map a
series of arrays, based on the number of rows, directly into your
matrix:
m = (0…rows).map {|r| Array.new(cols)}
Another way to do much the same thing is:
m =
rows.times { m << Array.new(cols) }
David
On Sat, 9 Nov 2002, Ted wrote:
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
Hi –
All of the replies say the same thing – this is good. My learning
project for Ruby is implementing a turning grille cipher. I want
to allocate a n*m matrix where n and m are read from stdin.I have the n (the rows) array, no sweat. But the m part (the
columns) is rather elusive.Here’s my latest code:
@m = Array.new(@rows)
@M = @m.each {|row| @m[row] = Array.new(@cols)}Try:
matrix = Array.new(@rows, Array.new(@cols))
The problem with that is that each row ends up being the same
object:
cols,rows = 3,5
m = Array.new(rows, Array.new(cols))
m[1][1] = “hello”
p m[2][1] # => “hello”
I’m not sure whether there’s a plan afoot to enable a proc-calling
version of this (with which you could create a separate object each
time).
David
On Sat, 9 Nov 2002, Austin Ziegler wrote:
On Sat, 9 Nov 2002 08:18:31 +0900, Ted wrote:
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
Hi –
On Sat, 9 Nov 2002 dblack@candle.superlink.net wrote:
m = (0…rows).map {|r| Array.new(cols)}
Whoops, see Gennady’s post where he does this without the extraneous
block variable
m = (0…rows).map { Array.new(cols) }
David
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
Austin Ziegler austin@halostatue.ca writes:
matrix = Array.new(@rows, Array.new(@cols))
Um… won’t work.
irb(main):027:0> matrix=Array.new(5, Array.new(6))
[[nil, nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil, nil]]irb(main):028:0> matrix[0].id
537855732
irb(main):029:0> matrix[1].id
537855732
irb(main):030:0> matrix[3].id
537855732
YS.
matrix = Array.new(@rows, Array.new(@cols))
The problem with that is that each row ends up being the same
object:
This may help:
@m = (0 … @rows).collect { Array.new @cols }
Gennady.
----- Original Message -----
From: dblack@candle.superlink.net
To: “ruby-talk ML” ruby-talk@ruby-lang.org
Sent: Friday, November 08, 2002 3:38 PM
Subject: Re: Multi-dimensional (like 2) arrays in Ruby
David
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
Hi –
On Sat, 9 Nov 2002, Gennady F. Bystritsky wrote:
@m = (0 … @rows).collect { Array.new @cols }
You’d want the ‘…’ operator, though, assuming @rows contains the
number of rows you want (rather than the 0-based index of the top
row).
David
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
