# Ad-hoc equality test for struct after definition

**URL:** <https://discourse.julialang.org/t/ad-hoc-equality-test-for-struct-after-definition/4615>\
**Category:** General Usage\
**Tags:** question\
**Created:** [July 3, 2017, 1:12pm UTC](https://discourse.julialang.org/t/ad-hoc-equality-test-for-struct-after-definition/4615 "2017-07-03T13:12:41Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![RogerP](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rogerp/32/17496_2.png) [@RogerP](https://discourse.julialang.org/u/RogerP)\
**Post date:** [March 26, 2021, 10:55am UTC](https://discourse.julialang.org/t/ad-hoc-equality-test-for-struct-after-definition/4615/12 "2021-03-26T10:55:25Z")

</div>

Just for the sake of it. This is what has gone into my `runtests.jl` for checking whether two structs are the same (or nearly the same if they have Floats). It’s ugly, doesn’t cover all types, but it only takes a few μs to run. (You don’t need to initialize `test` outside the function anymore.

```julia
function chkFieldNames!(x::S, y::T, icount=0, depth=0; test::Vector{Bool} = Vector{Bool}(undef,0), max_call=50) where {S, T}
    atol = 1e-5 # Resisted temptation to make an argument that is recursively passed around.
    if icount == 0 && depth == 0
        global test = Vector{Bool}(undef,0)
        println("Test initialised")
    end
    tx = typeof(x)
    ty = typeof(y)
    if tx == ty && depth < max_call
        for i in fieldnames(tx)  
            gx = getfield(x, i)
            gy = getfield(y, i)
            tgx = typeof(gx)
            if isprimitivetype(tgx)
                #println("Primitive type: ", tgx)
                if tgx <: AbstractFloat
                    push!(test, isapprox(gx, gy, atol=atol))
                else
                    push!(test, gx == gy)
                end
            elseif tgx <: AbstractArray
                #println("AbstractArray type: ", tgx)
                if ndims(gx) == ndims(gy)
                    push!(test, isapprox(gx, gy, atol=atol))
                else
                    push!(test, 0)
                end
            elseif tgx <: String
                #println("String type: ", tgx)
                push!(test, gx == gy)
            else
                depth += 1
                #icount != 0 || depth == 1 && println("Non-primitive type: ", tgx)
                chkFieldNames!(gx, gy, icount, depth, test=test)
            end
        end
    else
        if depth >= max_call 
            @warn "Run-away search -- self referential types?"
            return test
        else μ
            println("Unequal types: ", tx, " and ", ty)
            push!(test, 0)
        end
    end
    icount += length(test)
    #icount != 0 && println("Count = ", icount)
    return test
end           

```

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