invenia/layerdicts.jl

Layered dictionary lookups for Julia

LayerDicts

LayerDict is an Associative type that wraps a series of other associatives (e.g. Dicts). When performing a lookup, a LayerDict will look through its associatives in the order they were passed to the constructor until it finds a match. LayerDicts are immutable—you cannot call setindex! on them. However, you can update its wrapped associatives and those changes will be reflected in future lookups.

Example

using LayerDicts

dict1 = Dict{Symbol, Int}(:foo => 1, :bar => 1)
dict2 = Dict{Symbol, Int}()
dict3 = Dict{Symbol, Int}(:bar => 3, :baz => 3)

ld = LayerDict([dict1, dict2, dict3])
@assert ld[:foo] == 1
@assert ld[:bar] == 1
@assert ld[:baz] == 3
ld[:quuz]  # throws a KeyError

layerdicts.jl's Issues

Relax setindex! restriction

you cannot call setindex! on them

Finding this package, it seems to be exactly what I was thinking of implementing.

LittleDict is (ordered and) fast, up to a point, so I was thinking, having OrderedDict as a fallback, to prevent O(n). It seems to me you would have to bypass the abstraction, and can still do that, to update the (two, in my case) underlying dicts.

I guess I could reuse your code, wrap it in a package, or in my case, for Base not really.