Hi list
I was just bitten very recently by a subtlety of Ruby I had completely
forgotten about.
I thought it might be a challenge to use this subtlety in order to
make the following test (the attached file contains the same code of
course) work:
----------------------------------- 8< -----------------------------------
require 'test/unit'
user\_params = ARGV\[0\.\.1\]
class RRR\_002\_Methods < Test::Unit::TestCase
def test\_params\_without\_digits
assert /^\\D\+/ === $user_params.first, user\_params\.first
assert /^\\D\+/ === $user_params.last, $user_params.last
end
def test_rrr002
class << the_answer = Class::new
def answer base=10
42.to_s base
end
end
assert_equal "42", the_answer.answer
assert_equal "22", the_answer.answer( 20 )
rrr002.rb (914 Bytes)
···
#
# And now a little challange 
#
class << first_answer = Class::new( the_answer )
def answer base = 2
"[" << eval( $user_params.first ) << "]"
end
end
class << second_answer = Class::new( the_answer )
def answer base = 2
"[" << eval( $user_params.last ) << "]"
end
end
assert_equal "[101010]", first_answer.answer
assert_equal "[42]", second_answer.answer
end
end
----------------------------------- 8< -----------------------------------
As you can see digits are not allowed as parameters of the program.
Apart from the solution I would like to show, there is a completely
different one (not really very interesting but maybe a challange for
newbies), I could have blocked it easily enough by restricting the
length of the parameters but why spoil the fun ;).
Take the hint, the solution is a short one, much less than the 132
characters of the second solution.
But maybe there are even more solutions than these two.
Have fun
Robert
The following whitespace is intentional of course
--
http://ruby-smalltalk.blogspot.com/
---
Whereof one cannot speak, thereof one must be silent.
Ludwig Wittgenstein
