There is also the issue of locales and the radix char when non-integer values are used with multidimensional hash keys.

If one has coordinates 

[5,   5.5]
[5.5, 5  ]

[download]
then using the multidimensional hash approach in a locale where both $; and the radix char are a comma would result in ambiguous keys: 
{5,5,5}
{5,5,5}

[download]

I know the original post specifies signed ints, so I'm just being more generic here. I also haven't checked if there is locale specific behaviour of $;

In reply to Re^4: Fastest way to lookup a point in a set by swl
in thread Fastest way to lookup a point in a set by eyepopslikeamosquito

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