From: Dido Sevilla Date: 2007-10-23T13:38:15+09:00 Subject: Re: recursive array On 10/23/07, Simon Schuster wrote: > also, I'm interested in what is going on "behind the scenes" here. is > a[4][4][4][4][0] actually reaching in 4 levels deep? Well, what seems to have happened here is you created what amounts to a cyclic graph using the array. Every time you get the 4th index of a, you get back a itself. It's not exactly reaching in four levels deep but more accurately referencing itself four times. It's as if you created an array of pointers in C, and had some element in the array be a pointer back to the array itself. There are many uses for data structures of this type, as formal computer science is rife with graphs and the algorithms to deal with them. For instance, you could use such a structure as the internal representation of a state machine of some kind (finite automaton, pushdown automaton, linear bounded automaton, or even a Turing machine) , with each state being represented by an array, the inputs being indexes into the array, and the values of the array the new states the machine enters when a particular input is received. This is the simplest example I could think up off the top of my head, but read any decent book on algorithms and data structures and you'll find hundreds more. -- 普通じゃないのが当然なら答える私は何ができる？ 普通でも普通じゃなくて感じるまま感じることだけをするよ！ http://stormwyrm.blogspot.com