Here is a very short Julia code that gives a mysterious error message in
the latest build (952). Is it an error in my code or a bug in Julia? (In
addition to the answer to this question, I would also like help with the
code design question in my previous posting of two hours ago.)
Thanks,
Steve
module testnestparam2
typealias ADict{K,D} Array{Dict{K,D},1}
function makeADict()
a = ADict([[-9=>"a"],[15=>"b"]]) #line 6
println("a[1][-9] = ", a[1][-9])
end
end
julia> testnestparam2.makeADict()
ERROR: type: makeADict: in apply, expected Function, got
Type{Array{Dict{K,D},1
}
in makeADict at
c:\Users\vavasis\Documents\Projects\qmg21\julia\testnestparam2
jl:6
On Tuesday, October 7, 2014 10:05:09 AM UTC-4, [email protected] wrote:
>
> Thanks for the explanation! Although I think I understand your answer,
> I'm not sure how to define the types to accomplish my goal.
>
> * a Token should have two parts, a container and a semitoken, both abstract
>
> * an SDToken should be a specialization of Token in which the container
> portion is SortedDict{K,D} for a specific K,D and the semitoken portion is
> IntSemiToken (both parts concrete)
>
> * Some functions take SDToken's as input. These should be generic, i.e.,
> work for all choices of K,D.
>
> * There are also generic functions that return SDTokens as output (in
> which K and D are determined from the input args).
>
> Can I write typealias SDToken{K,D} Token{SortedDict{K,D},IntSemiToken}? I
> tried this and got an unexpected error message:
>
> ERROR: type: test1: in apply, expected Function, got
> Type{Token{SortedDict{K,D},
> IntSemiToken}}
> in test1 at
> c:\Users\vavasis\Documents\Projects\qmg21\julia\testnestparam.jl:32
>
> (No 'apply' in my code!) And in any case, even if I could write this, I'm
> not sure it solves the problem.
>
> -- Steve
>
>
>
> On Tuesday, October 7, 2014 2:15:01 AM UTC-4, Jutho wrote:
>>
>> I don't see the problem regarding point one.
>>
>> A type with parameters, as your SortedDict{D,K}, becomes an abstract type
>> when the parameters are unspecified, e.g. SortedDict, but this is indeed
>> printed/formatted with unspecified parameters put back (I guess with the
>> name as you defined them), e.g. as SortedDict{D,K}.
>>
>> Regarding point 2, this relates to the invariance of parametric types.
>>
>> isa(t2,Token{SortedDict, IntSemiToken})
>> will return false, because
>> Token{SortedDict{Int64,ASCIIString},IntSemiToken} <: Token{SortedDict,
>> IntSemiToken}
>> is false. There are many discussions regarding this both on the forum and
>> I guess in the manual. Search for invariance versus covariance of
>> parametric types.
>>
>>
>> Op dinsdag 7 oktober 2014 04:42:12 UTC+2 schreef [email protected]:
>>>
>>> The code below is an excerpt from a more complicated code I am writing.
>>> It contains a parametrized type in which the parameter is itself another
>>> parametrized type. I have attached the printout (0.4.0-dev+323). Notice
>>> the error message at the end. My questions are:
>>>
>>> (1) How is it possible that the type of t includes dummy parameters K
>>> and D, which aren't real types at all?
>>>
>>> (2) Why is Julia not able to match t2 but it is able to match t to the
>>> signature of test0()?
>>>
>>> Thanks,
>>> Steve Vavasis
>>>
>>>
>>> julia> testnestparam.test1()
>>> typeof(t) = Token{SortedDict{K,D},IntSemiToken}
>>> typeof(t2) = Token{SortedDict{Int64,ASCIIString},IntSemiToken}
>>> methods(test0) = # 1 method for generic function "test0":
>>> test0(i::Token{SortedDict{K,D},IntSemiToken}) at
>>> c:\Users\vavasis\Documents\Projects\qmg21\julia\testnestparam.jl:28
>>> ERROR: `test0` has no method matching
>>> test0(::Token{SortedDict{Int64,ASCIIString},IntSemiToken})
>>> in test1 at
>>> c:\Users\vavasis\Documents\Projects\qmg21\julia\testnestparam.jl:38
>>>
>>>
>>> module testnestparam
>>>
>>> immutable IntSemiToken
>>> address::Int
>>> end
>>>
>>> immutable Token{T, S}
>>> container::T
>>> semitoken::S
>>> end
>>>
>>> # take a token apart
>>> semi(i::Token) = i.semitoken
>>> container(i::Token) = i.container
>>>
>>> # put a token back together
>>> assemble(m, s) = Token(m,s)
>>>
>>> type SortedDict{K, D} <: Associative{K,D}
>>> bt::Dict{K,D}
>>> end
>>>
>>> typealias SDToken Token{SortedDict, IntSemiToken}
>>>
>>> sdtoken_construct(m::SortedDict,int1::Int) =
>>> SDToken(m, IntSemiToken(int1))
>>>
>>> test0(i::SDToken) = nothing
>>>
>>> function test1()
>>> s = SortedDict([1=>"a",2=>"b"])
>>> t = sdtoken_construct(s, 0)
>>> t2 = assemble(t.container, t.semitoken)
>>> println("typeof(t) = ", typeof(t))
>>> println("typeof(t2) = ", typeof(t2))
>>> println("methods(test0) = ", methods(test0))
>>> test0(t)
>>> test0(t2) #Line 38
>>> end
>>>
>>> end
>>>
>>>
