Leah-- that is very helpful, thanks!
I rewrote the code testnestparam with parameters everywhere (see below),
and now it works. It does not work, however, if I define test0(i::SDToken)
= nothing (method not found error). I don't understand why that is. Isn't
any instance of SDToken{K,D} for a specific choice {K,D} a subtype of
abstract unparametrized SDToken? In this case, why can't Julia match
test0 when it is unparametrized?
More generally, is there a writeup on parametrized types that goes into
more detail than the manual and has many examples? I keep making mistakes
with them because my understanding is incomplete.
Thanks,
Steve
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{K,D} Token{SortedDict{K,D}, IntSemiToken}
sdtoken_construct{K,D}(m::SortedDict{K,D}, int1::Int) =
SDToken{K,D}(m, IntSemiToken(int1))
test0{K,D}(i::SDToken{K,D}) = nothing
# test0(i::SDToken) = nothing # This variant fails. Why?
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)
end
end
On Tuesday, October 7, 2014 12:58:30 PM UTC-4, Leah Hanson wrote:
>
> You need to fully specify TDict when using it's constructor:
>
> ~~~
> julia> module testnestparam2
>
> immutable Token{S,T}
> m::S
> t::T
> end
>
> typealias TDict{K,D} Token{Dict{K,D}, Int}
>
> function makeADict()
> a = TDict{Int64,String}([1=>"a",2=>"c"], 5)
> end
>
> end
> Warning: replacing module testnestparam2
>
> julia> testnestparam2.makeADict()
> Token{Dict{Int64,String},Int64}([2=>"c",1=>"a"],5)
> ~~~
>
> On Tue, Oct 7, 2014 at 11:41 AM, <[email protected] <javascript:>>
> wrote:
>
>> Oops, sorry, in my last posting there was obviously an error in my code
>> because I used the wrong syntax to call an array constructor. Here is
>> another example where now I am using the correct constructor syntax (I
>> think?). But I still get the same error message concerning 'apply'.
>>
>> module testnestparam2
>>
>> immutable Token{S,T}
>> m::S
>> t::T
>> end
>>
>> typealias TDict{K,D} Token{Dict{K,D}, Int}
>>
>> function makeADict()
>> a = TDict([1=>"a",2=>"c"], 5)
>> end
>>
>> end
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On Tuesday, October 7, 2014 12:29:49 PM UTC-4, [email protected] wrote:
>>>
>>> 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
>>>>>>
>>>>>>
>
