Re: Array/Matrix Help

[Adam Beneschan <adam@irvine.com>]

On Tuesday, April 3, 2012 7:55:26 PM UTC-7, Will wrote:
> I need to create function Create_Matrix that  accepts four
> Int_Arrays.  It must determine if all 4 Int_Arrays are of equal length
> and then creates and returns an Int_Matrix of the 2 or more arrays
> with equal length.
> 
> Here is what I am thinking so far, I believe it will work but seems
> inefficient and I am looking for efficiency in my coding.  I am not
> sure how to determine which ones are equal other than a bunch of if/
> elsif statement that cover every possible combination of them being
> equal then write the code that will create the matrix for that given
> combination of arrays.   Any ideas on something better than the
> following.  I am assuming that there will not be 2 sets of arrays that
> are equal (i.e. 2 arrays of length 5 , and another 2 of length 7)
> There would only be 1 common length.
> 
>   function Create_Matrix (A, B, C, D : Int_Array) return Int_Matrix
> 
>        begin
> 
>            if A'Length = B'Length and A'Length = C'Length and A'Length
> = D'Length then
> 
>  Then continue to do this all the way until I cover every combination
> of 2 or more arrays that are equal length and then whichever if
> statement it satisfies create the Int_Matrix by each array being its
> own line inside the matrix.
> 
> Can anyone offer help or ideas.  Any hints/help is greatly
> appreciated... I prefer that over just giving me the code.

I don't think there's a good way to do this except with a bunch of if/then/elses.  If you're super-concerned about efficiency, you might want to create a 6-bit integer where each bit corresponds to one of the six pairs of comparisons (add 1 if A'Length=B'Length, add 2 if A'Length=C'Length, add 4 if something...) and then do a CASE on the integer to cover all 64 possibilities.  But that's an ugly way to write this just to eliminate a few nanoseconds.

                    -- Adam