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Re: ChainMap of Hashes on CPAN?

by sundialsvc4 (Abbot)
on Mar 25, 2013 at 15:17 UTC ( #1025323=note: print w/replies, xml ) Need Help??

in reply to ChainMap of Hashes on CPAN?

The only time where I have seen this done is where there were several different name-spaces in play, and they did have a visibility-hierarchy relative to one another (such as local vs. global symbols), and the entirety of a name-space was created and then thrown away many times as the program ran.   You unquestionably could human-notice the time that it took to run through all the hashes on a hash-miss, but it was a price to be paid.

Absent such considerations, though, I generally approach this problem by simply creating one hash into which every symbol encountered is added, but never removed.   The symbol’s hash-entry points to a record/object in which the various meanings-of-the-moment are maintained in a list.   (A symbol might appear in the hash but have no current meanings at all, and in the application that I am thinking about, the same names tended to be re-used many times.   The price of insertion was paid but once, and the price of removal from the hash, not at all.)

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[ambrus]: Today I accidentally cut my hand while carrying a computer. On the display part of the motherboard that sticks out at the back of the chasis and has ports, there's this thin metal sheet with holes cut for the ports, to guide plugs into the sockets.
[ambrus]: This sheet has sharp needle-like parts, 0.004 long and less than 0.001 wide, that can get bent to point outwards, and one of these cut into my palm when I lifted the box.
[ambrus]: So now when I choose what motherboard to buy for my new home computer, I have one more specific property to guide me. Useful, because there's so many different boards to choose from.

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