Priority in chained comparisons in Julia, does "var1 && var2 != 1" mean "(var1 and var2) != 1"?

Question

I have a questions regarding the chained comparisons in Julia. I read this section in the manual but it is still unclear.

In Julia, does this:

if var1 && var2 != 1

mean this (in Python):

if (var1 and var2) != 1:

Thank you!

Answer 1

From what I could read on that page and a linked page (http://docs.julialang.org/en/latest/manual/control-flow/#man-short-circuit-evaluation), no. The order of operations is different. It ends up like this:

if (var1) && (var2 != 1)

First, the xscalar variable gets checked for a value that would satisfy an if statement, as if you did

if var1

Then, if, and only if that is accepted, does the next part get evaluated:

if var2 != 1

In other words, these two statements are roughly equivalent:

if var1
    if var2 != 1

and

if var1 && var2 != 1

(forgive the lack of julia syntax knowledge)

A python equivalent of this would be:

if var1 and var2 != 1:

or, with parentheses to show with more clarity,

if (var1) and (var2 != 1) :

Answer 2

You can always quote an expression to see how the parser interprets it:

julia> :(var1 && var2 != 1)
:(var1 && (var2!=1))

In this case, the != binds more tightly than the &&. This is standard precedence in languages that have these two operators) such as C and Java.