Hi,
I'm a bit confused on why the follow code fails:
abstract Country
immutable US <: Country; pct::Real end
immutable CA <: Country; pct::Real end
immutable DE <: Country; pct::Real end
abstract AbstractAsset{Listed<:Country,Origin<:Country} # line 6
type Stock{Listed,Origin} <: AbstractAsset{Listed,Origin}
listed::Type{Listed} # the country of the exchange (where it was
purchased)
origin::Type{Origin} # the country the stocks are from
end
type Account{A<:AbstractAsset} # line 12
holdings::AbstractVector{A}
end
for stocks in Any[[Stock(US,US)], [Stock(US,US), Stock(US,US)], [Stock(CA,
US), Stock(CA, CA)]] # line 16
@show typeof(stocks)
Account(stocks)
end
The error output is:
typeof(stocks) => Array{Stock{US,US},1}
typeof(stocks) => Array{Stock{US,US},1}
typeof(stocks) => Array{Stock{Listed,Origin},1}
ERROR: `Account{A<:AbstractAsset{Listed<:Country,Origin<:Country}}` has no
method matching
Account{A<:AbstractAsset{Listed<:Country,Origin<:Country}}(::Array{Stock{Listed,Origin},1})
in anonymous at no file:18
in include at ./boot.jl:245
in include_from_node1 at loading.jl:128
in process_options at ./client.jl:285
in _start at ./client.jl:354
while loading type_of_types.jl, in expression starting on line 16
The fix seems to be to change line 7 to:
type Stock{Listed<:Country,Origin<:Country} <: AbstractAsset{Listed,Origin}
then the output is:
typeof(stocks) => Array{Stock{US,US},1}
typeof(stocks) => Array{Stock{US,US},1}
typeof(stocks) => Array{Stock{Listed<:Country,Origin<:Country},1}
These changes to line 7 would seem to be redundant because Listed and
Origin already must be a Country because of line 6 -- I tested setting
"Stock.listed" to a currency and it indeed fails (as expected because of
line 6). I get confused about how the parametric types resolve their types
and I feel that I'm missing some key concept. Can someone help me
understand what is going on here? Debugging "has no method matching"
errors comes up quite often for me.
Thanks,
Glen
