typealias constructors

[Krishna Subramanian]

I would like to know how to do something like this-

typealias Corpus Array{Int,1}

and write a constructor for it. Currently, if I do -

Corpus() = Array(Int,0)

I get-

ERROR: cannot define function Corpus; it already has a value

I am sure others have encountered this problem before. I went through https://github.com/JuliaLang/julia/issues/1470 but I am still not able to figure out what is the issue involved. 

Thanks,

Krishna

[Mauro]

You need to be on 0.4 to do this.

[Krishna Subramanian]

Sorry for the bother-

I just resolved the issue like this-

import Base.push!

typealias Corpus Array{Int,1}

corpus = Int[]::Corpus

push!(corpus,1)

push!(corpus,2)

@assert typeof(corpus) == Corpus

@assert typeof(corpus) == Array{Int,1}

Thanks,

Krishna

[Vincent Lostanlen]

Is there a way to make this backwards compatible with latest v0.3 ? I find typealias constructors extremely handy to extend the behavior of existing recursive constructors (LinkedList here).
Here is a minimal use case requiring DataStructures and Compat:

immutable Literal
    symbol::Symbol
    level::Int
end
typealias SymbolInt @compat(Tuple{Symbol,Int})
Literal(tup::SymbolInt) = Literal(tup[1], tup[2])
Literal(sym::Symbol) = Literal(sym, 1)

typealias MyList LinkedList{Literal}
MyList() = nil(Literal)
MyList(head::Literal, tail...) = cons(head, VariableKey(tail...))
MyList(head::Union(SymbolInt,Symbol), tail...) = cons(Literal(head), VariableKey(tail...))

On v0.4, this code makes the MyList type a synonym of LinkedList{Literal}, without having to explicitly construct a Literal object for every element in the list a priori.
What can I do ?

Vincent.

[Vincent Lostanlen]

Errata : here is a MWE that actually works.

immutable Literal
    symbol::Symbol
    level::Int
end
typealias SymbolInt @compat(Tuple{Symbol,Int})
Literal(tup::SymbolInt) = Literal(tup[1], tup[2])
Literal(sym::Symbol) = Literal(sym, 1)

typealias MyList LinkedList{Literal}
MyList() = nil(Literal)

MyList(head, tail...) = cons(Literal(head), MyList(tail...))



After running this on v0.4, MyList(:a, (:b, 2)) yields
list(Literal(:a,1), Literal(:b,2))
which is exactly what I want: a list of Literals that support mixed syntax for element construction.
Is it possible to do this on prior versions ?

Vincent.