show(io::IO, custom matrix) is not called?

General Usage
1

Hi,

I’m trying to show my custom matrix type to display by overloading the Base.show method, but it doesn’t call the overloaded method. The following is a reproducible code:

# https://github.com/BioJulia/BioSymbols.jl
import BioSymbols: DNA

struct PWM{T,S<:Real} <: AbstractMatrix{S}
    # symbol type (DNA or RNA)
    typ::Type{T}
    # score matrix (row: symbols, column: position)
    data::Matrix{S}
end

function Base.size(pwm::PWM)
    return size(pwm.data)
end

function Base.getindex(pwm::PWM, i::Integer, j::Integer)
    return getindex(pwm.data, i, j)
end

function Base.show(io::IO, pwm::PWM{DNA})
    compact(x) = string(x ≥ 0 ? " " : "", sprint(showcompact, x))
    cells = hcat(['A', 'C', 'G', 'T'], compact.(pwm.data))
    width = maximum(length.(cells), 1)
    print(io, summary(pwm), ':')
    for i in 1:size(cells, 1)
        println(io)
        print(io, ' ', rpad(cells[i,1], width[1]+1))
        for j in 2:size(cells, 2)
            print(io, rpad(cells[i,j], width[j]+1))
        end
    end
end

I expect I see ACGT characters on the leftmost column:

julia> pwm = PWM(DNA, randn(4, 5))  # not overloaded?
4×5 PWM{BioSymbols.DNA,Float64}:
  2.05598    -1.48329   -0.909718   -0.915152  -0.199301
 -1.65405     0.456539   0.0655709  -1.18943    0.158246
  0.0463668  -0.647083  -0.430253   -0.251961   1.59043
 -0.333135    1.01648   -0.665186    0.922921   0.199385

julia> pwm isa PWM{DNA}  # pwm is actually an object of PWM{DNA}
true

julia> show(pwm)   # but this is okay
4×5 PWM{BioSymbols.DNA,Float64}:
 A  2.05598   -1.48329  -0.909718  -0.915152 -0.199301
 C -1.65405    0.456539  0.0655709 -1.18943   0.158246
 G  0.0463668 -0.647083 -0.430253  -0.251961  1.59043
 T -0.333135   1.01648  -0.665186   0.922921  0.199385

Is this a bug of Julia or am I missing something?

Thank you.

2

If my memory doesn’t fail me, the following should work

function Base.show(io::IO, ::MIME"text/plain", pwm::PWM{DNA})
    # ...
end
1 Like
3

That’s because AbstractMatrix has custom methods for both show(io, x) and show(io, ::MIME"text/plain", x), and the latter is used for displaying results in the REPL.

4

Than you and @Evizero! That makes sense.