[julia-users] Creating a show method for type alias

[Ben Ward]

Hi, I have implemented a basic immutable type with a type alias for a 
vector of said type:

immutable CIGAR
    OP::Operation
    Size::Int
end


function CIGAR(op::Char, size::Int)
    return CIGAR(Operation(op), size)
end


function convert(::Type{String}, cigar::CIGAR)
    return "$(cigar.Size)$(Char(cigar.OP))"
end


function show(io::IO, cigar::CIGAR)
    write(io, convert(String, cigar))
end


typealias CIGARString Vector{CIGAR}


function convert(::Type{CIGARString}, str::String)
    matches = matchall(r"(\d+)(\w)", str)
    cigarString = Vector{CIGAR}(length(matches))
    @inbounds for i in 1:length(matches)
        m = matches[i]
        cigarString[i] = CIGAR(m[end], parse(Int, m[1:end-1]))
    end
    return cigarString
end


macro cigar_str(str)
    return CIGARString(str)
end

I also want to define a show method for the alias CIGARString, so as it is 
converted to a string that can be used with a show method:

function convert(::Type{String}, cigarString::CIGARString)
    outString = ""
    for cigar in cigarString
        outString *= String(cigar)
    end
    return outString
end


function show(io::IO, cigarstr::CIGARString)
    write(io, convert(String, cigarstr))
end

However the output a see on the REPL is:

*3-element Array{Bio.Align.CIGAR,1}:*

* 5M*

* 5N*

* 5M*

So, rather than the show method for CIGARString being called, the show 
method for CIGAR is being called repeatedly for every element in the 
CIGARString vector. How do I get Julia to use the show method I want for 
CIGARString?

Thanks.