Re^3: The Definitive Unit Conversion Script


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Re^3: The Definitive Unit Conversion Script

by Aristotle (Chancellor)

on Dec 13, 2002 at 19:37 UTC ( [id://219716]=note: print w/replies, xml )

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in reply to (tye)Re2: The Definitive Unit Conversion Script
in thread The Definitive Unit Conversion Script

"Definitive" in the sense that it effortlessly converts into all related units, not in the amount of units handled. :)

Of course it would be nice to add some limited parsing and intrinsic "understanding" of units and I can see how I'd go about implementing the basic idea (split into numerator and denominator, convert, divide), but how complex a unit specification should it be able to handle? I don't want to add so much weight that it turns into a small expression evaluator. I'm thinking one unit in the numerator, one in the denominator, and one power given for each sounds like a viably complex, sufficiently flexible spec.

Makeshifts last the longest.

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(tye)Re3: The Definitive Unit Conversion Script
by tye (Sage) on Dec 13, 2002 at 20:20 UTC

This doesn't have to be complicated. Split on * and before /, then check for /\^\d+$/:

    my @units= split m#(?<=.)(?:(?=/)|\*)#, $units, -1;
    my %power;
    for my $unit (  @units  ) {
        my $power= 1;
        if(  $unit =~ s#\^(\d+)$##  ) {
            $power= $1;
        }
        if(  $unit =~ s#^/##  ) {
            $power= -$power;
        }
        $power{$unit} += $power;
    }
    # ...
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(Updated and tested.)

tye

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