nulls.jl

# 0.6 Approach
using BenchmarkTools
using NullableArrays

n = 10_000_000

x = rand(n)
y = NullableArray{Float64}(n)
for i in 1:n
    if !iseven(i)
        y[i] = x[i]
    end
end

sum(x)
sum(y)

@benchmark sum($x)
@benchmark sum($y)

# 0.7 Approach
using BenchmarkTools

n = 10_000_000

x = rand(n)
y = [ifelse(iseven(i), missing, x[i]) for i in 1:n]

sum(x)
sum(y)

@benchmark sum($x)
@benchmark sum($y)