Re: [Haskell-cafe] How can i safely change the value of specified key ?

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f xs = (2,2222) : filter ((/=2) . fst) xs It works but not general as `f` still needs to change other value according to the "KEY". Maybe Data.List will supply what i need.

Ketil Malde-5 wrote:

zaxis writes:

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value <- readIORef aaa writeIORef aaa (f value)

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then aaa will *point to* a new value.

Exactly. That's what IORefs are, references pointing to contents that can be changed in the IO monad.

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The original value will be Garbage Collected, right ?

Yes, unless something else is holding on to it.

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Is [(1,1),(2,2),(3,3)] been regarded as a hash?

It's a list of pairs. You can treat it as an association list using e.g. 'lookup' from Data.List, if that's what you mean.

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If not, what is the best way to change it to [(1,1),(2,2222),(3,3)] in function `f` ?

Not sure if there's anything in Data.List, but you could do something like:

f xs = (2,2222) : filter ((/=2) . fst) xs

-k -- If I haven't seen further, it is by standing in the footprints of giants _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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