Supporting dependent loop ranges in comprehensions

[KristofferC]

Simple example,

this works:

for i in 1:3, j in 1:i
    println(i + j)
end

this fails with UndefVarError on i.

[i+j for i in 1:3, j in 1:i]

Would it be possible to support the syntax of the second version?

[nalimilan]

I don't see how it could work given that it wouldn't return a standard (rectangular) array. Would you expect it to return a triangular matrix? But then there is no general solution for arbitrary expressions of j.

[KristofferC]

I forgot that comprehensions don't just return a one dimensional array. What I wanted would just be the expression in a straight list, like [2,3,4,4,5,6]

[JeffBezanson]

Dup of #4867