Le vendredi 20 février 2015 à 18:40 -0800, Tom Colvin a écrit :
> I get a "key not found" error even though the key is clearly in there.
> Here's a stripped down version of the code that produces the error:
>
> # Define my custom type
> type Test
> act::Array{Int64}
> obs::Array{Int64}
> end
>
> # Have to define an equality operator for the new type
> import Base
> Base.(:(==))(a::Test, b::Test) = (
> function (a::Test, b::Test)
> (a.act == b.act) && (a.obs == b.obs)
> end ) (a,b)
>
> # Make a Test, use it as a key in a dictionary,
> # then make a new test that is known to be in the dict
> myTest = Test([1], [1])
> test2ID = Dict([myTest=>1])
> myTestCopy = deepcopy(myTest)
>
> # These work
> test2ID[myTest] # 1
> myTest in keys(test2ID) # true
> myTestCopy in collect(keys(test2ID)) # true
> myTest == myTestCopy # true
>
> # These fail
> test2ID[myTestCopy] # error: key not found
> myTestCopy in keys(test2ID) # false
>
> So if I index with the original object that I created the dict from,
> then it works. If I have created a new and identical object, I get
> "key not found" when I index by the new object AND it doesn't appear
> in the keys() of the dictionary. Puzzlingly, if the keys() are
> collect()ed then it is indeed found.
>
> I suspect this is a bug, but wanted to check with the community before
> opening an issue on github. Am I doing something wrong?
For efficiency, during a dict lookup keys are not tested for equality
using ==, but using hashes. By default, types are hashed using the
memory address of the object. I think you need to define your custom
hash() function by recursively hashing its fields. See ?hash.
Regards
