Hey

I tried to Super Search this, and I posted it in the Chatterbox, but I got directed here. This is really about finding the most elegant solution to a problem that suggests several ugly answers to me.

I have an N X M matrix that gives an output value for a pair of input values, say $x and $y. Each row of the matrix represents a range of values (disjoint from the others) that $x might fall into. Similarly for columns and $y. Thus, each matrix entry corresponds to the pair of intervals that contain $x and $y.

The most obvious way to deal with this is to create nested conditionals or a bunch of && conditionals that account for $x and $y, but that's unspeakably ugly and takes N*M conditional statements.

Less ugly is making a multi-dimensional hash, keyed by interval ID (e.g. Interval 1, Interval 2...), and then just setting up conditionals to return the right pair of IDs for $x and $y. That reduces the problem to N+M conditionals, but that's still a lot.

I thought about trying to find a way to transform $x and $y into their interval IDs, but the interval boundaries are floats and the first and last intervals are <some_value and >some_other_value, which makes that transformation harder.

I was taught to avoid a long sequence of conditionals, so I have to wonder: Is there a more elegant solution to this? Perhaps a module? Or should I just banish N+M conditionals to a subroutine at the bottom?

Thanks in advance,

Hays

Update:I like jdporter's solution for making the conditionals prettier, but it still involves a bunch of conditionals (unless I misunderstand). I don't have current code, since I'm looking for the best approach, but as per Grandfather's request, here's what code might look like that corresponds to the two approaches I've described:

Here's the solution most obvious to me (and least elegant):

if ($x<1) {
    if ($y<2.5) {
        $z=4;
    } elsif ($y>=2.5 && $y<3.5) {
        $z=6;
    } elsif.....
} elsif ($x>=1 && $x<3.3) {
    if ($y<2.5) {
        $z=3
    }......

[download]

And here's the solution that reduces it to N+M conditionals:

if ($x<1) {
    $xkey=1;
} elsif ($x>=1 && $x<3.3) {
    $xkey=2;
}...

if ($y<2.5) {
    $ykey=1;
} elsif ($y>=2.5 && $y<3.5) {
    $ykey=2;
}...

$z=$hash{$xkey}{$ykey};

[download]

What else would help?

Update 2: Thanks, nevyn!

In reply to Getting around nested conditionals by hgolden

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