From: Mark Liang <mwql.aus@...>
Date: 2005-12-14T12:07:39+09:00
Subject: Undefined method

I've recently started learning Ruby, I cannot seem to locate the
cause of this error. Please pardon me if the answer is more
straightforward as it seems.

I've double-checked, blkcheck method works fine. I suspect the
problem lies with line 32, Blk.each ..., however, I don't see why
a problem should be there. Please help shed some light.

The error message:

../creat.rb:25:in `blkcheck': undefined method `[]' for nil:NilClass
(NoMethodError)
        from ./creat.rb:25:in `times'
        from ./creat.rb:25:in `blkcheck'
        from ./creat.rb:24:in `times'
        from ./creat.rb:24:in `blkcheck'
        from ./creat.rb:33:in `blkscheck'
        from ./creat.rb:32:in `each'
        from ./creat.rb:32:in `blkscheck'
        from ./creat.rb:45


The src:

      1 #!/usr/bin/ruby
      2
      3 Val = [1, 2, 3, 4, 5, 6, 7, 8, 9]
      4 Blk = [[0,0],[0,3],[0,6],[3,0],[3,3],[3,6],[6,0],[6,3],[6,6]]
      5
      6 def linescheck (tab)
      7    num = 0
      8    9.times { |i| num += 1 if tab[i].sort == Val }
      9    1 if num == 9
     10 end
     11
     12 def colscheck (tab)
     13    num = 0
     14    9.times do |i|
     15       tmp = []
     16       9.times { |j| tmp <<= tab[j][i] }
     17       num += 1 if tmp.sort == Val
     18    end
     19    1 if num == 9
     20 end
     21
     22 def blkcheck (tab, i, j)
     23    tmp = []
     24    3.times do |k|
     25       3.times { |l| tmp <<= tab[i+k+l][j+k] }
     26    end
     27    1 if tmp.sort == Val
     28 end
     29
     30 def blkscheck (tab)
     31    num = 0
     32    Blk.each do |i,j|
     33       num += 1 if blkcheck(tab,i,j)
     34    end
     35    1 if num == 9
     36 end
     37
     38 # Create the table of values
     39 val = []
     40 9.times do |i|
     41    val <<= Val
     42 end
     43
     44 #blkscheck(val)
     45 print "Hello world!\n" unless blkscheck(val)