On Fri, Jan 20, 2006 at 10:57:03PM +0900, Ruby Quiz wrote:
[...]
} The input to the function is a string containing the characters "T" (the
} top edge folded down to the bottom edge), "B" (bottom up to top), "R"
} (right to left) and "L" (left to right). Not every combination of those
} will be valid, so make sure you verify your input.
[...]
} To help clarify, here's a 2x2 example.
} 
} 	+-+-+
} 	|1|2|
} 	+-+-+
} 	|3|4|
} 	+-+-+
} 	
} 	fold("RB") => [3, 4, 2, 1]
} 	fold("TL") => [3, 1, 2, 4]
} 	fold("LR") => raise exception for invalid input 

Assuming it is only composed of [LRTB], is there any way in which the
string can be invalid other than too many folds in a particular dimension?

--Greg