print "squashed-circle" diamond

There's been a bit of a buzz about the Print-Diamond practice recently. I recall doing this a couple of years ago with Johannes Brodwall. In cyber-dojo naturally. We took a wrong turn and were making a thorough mess of it. I vividly recall Johannes saying:

This is too difficult. We're doing it wrong.

I love that. If it's difficult you're probably doing it wrong. We gave up and took a break. We got a really nice Indian take away. Then we went back to Print-Diamond. Very quickly we came up with a new idea. We imagined the diamond lying in the center of an x,y axis. The Print-Diamond of 'C' would therefore look like this:

       -2 -1  0 +1 +2

  -2    -  -  A  -  -    
  -1    -  B  -  B  -
   0    C  -  -  -  C
  +1    -  B  -  B  -
  +2    -  -  A  -  -

Viewed like this you can think of the Diamond as a sort of squashed circle with the A,B,C characters all lying on the circumference. From here it was a short step to this (Ruby):

(-2..+2).map{|row| 
  (-2..+2).map{|col| 
    row.abs + col.abs == 2 ? 'X' : '-'
  }.join
}

which, when puts'd gives:

--X--
-X-X-
X---X
-X-X-
--X--

And we knew we were on our way.
Let's hear it for Curry Driven Development!