Re: [julia-users] array with different column types

['Stéphane Laurent' via julia-users]

Hello everybody,

 Below I define two new types : Line and Poly. The Poly type is intended 
for stacking some lines.  

type Line

        a::Float64   # intercept

        b::BigFloat  # slope

        x1::BigFloat # x-coordinate of first vertex

        y1::BigFloat # y-coordinate of first vertex

        x2::BigFloat # x-coordinate of second vertex

        y2::BigFloat # y-coordinate of second vertex

        typ::Bool    # type of the line (true:upper, false:lower)

end


type Poly

        a::Vector{Float64}

        b::Vector{BigFloat}

        x1::Vector{BigFloat}

        y1::Vector{BigFloat}

        x2::Vector{BigFloat}

        y2::Vector{BigFloat}

        typ::Vector{Bool}

end



I also define the empty Poly:

emptyPoly = Poly(Array(Float64,0), Array(BigFloat,0), Array(BigFloat,0), 
Array(BigFloat,0), Array(BigFloat,0), Array(BigFloat,0), Array(Bool,0));



And a function to generate a new Line:

function newLine(a::Float64, b::BigFloat, typ::Bool)

        return Line(a, b, BigFloat(Inf), BigFloat(Inf), BigFloat(Inf), 
BigFloat(Inf), typ)

end



Now I define some macros but it seems that I'm doing something bad :

macro addLine(poly, line)

        for op = (:a, :b, :x1, :y1, :x2, :y2, :typ)

          @eval $poly.$op = [$poly.$op, $line.$op]

        end

end


macro removeLine(poly, index)

    for op = (:a, :b, :x1, :y1, :x2, :y2, :typ)

        @eval splice!($poly.$op, $index)

    end

end



There's something bad when I'm doing this:

D = newLine(0.4, BigFloat("1.5"), false)

poly = emptyPoly;

@addLine poly D



*Question 1:* I don't understand why the previous code changes the value of 
emptyPoly, as if poly and emptyPoly were linked:

julia> emptyPoly

Poly([0.4],[1.5e+00 with 256 bits of precision],[inf with 256 bits of 
precision],[inf with 256 bits of precision],[inf with 256 bits of 
precision],[inf with 256 bits of precision],[false])



*Question 2:* There's another problem when I'm using the removeLine macro 
inside a loop :

@addLine poly D

@addLine poly D

for index = [1 2]

    @removeLine(poly, index) 

end


This code doesn't work and generates the error message "index not found".