This is essentially the same as substr and a hash, but will run faster. Forgive the funky pseudocode. 

sub is_compatible {
    my T, B;
    foreach i from 0 .. stringlen {
        next if top[i] eq bottom[i]
        if top[i] is a digit
            return NOT COMPATIBLE if bottom[i] is a digit
            T |= top[i]
        if bottom[i] is a digit
            B |=  bottom[i]
    }
    return T&B ? NOT COMPATIBLE : COMPATIBLE
}

[download]

Assumptions: your "digits" are weakly fewer in number than your integer1 width. If by digit you really do mean 0 .. 9, I think this obtains on all the machines Perl runs on. In which case you can also optimize "is a digit" with low-level ASCII checks. Also, you should probably only split each string once instead of seeking into it. If this isn't fast enough, this is a good candidate for inlining in c.

1 More precisely, whatever does efficient bitwise arithmetic.

In reply to Re: Comparison by position and value by gaal
in thread Comparison by position and value by BrowserUk

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