Re: Evaluation order of block pass versus arguments

Sorry, I realized there's no call for action here. Can we get an 
official ruling that the 1.9 evaluation order is the "correct" one, and 
consider the 1.8 behavior to be a quirky implementation artifact?

Charles Oliver Nutter wrote:
> I was writing up some specs for evaluation order today and discovered 
> something rather interesting:
> 
>   before :each do
>     @obj = Object.new
>     def @obj.foo(a, b, &c)
>       [a, b, c ? c.call : nil]
>     end
>   end
> 
>   it "evaluates block pass before arguments" do
>     a = 0
>     p = proc {true}
>     @obj.foo(a += 1, a += 1, &(a += 1; p)).should == [2, 3, true]
>     a.should == 3
>   end
> 
>   it "evaluates block pass before receiver" do
>     p1 = proc {true}
>     p2 = proc {false}
>     p1.should_not == p2
> 
>     p = p1
>     (p = p2; @obj).foo(1, 1, &p).should == [1, 1, true]
>   end
> 
> This was unexpected for me. Argument order being left-to-right seems 
> reasonable, and I think it's what most people would expect looking at 
> the code. But having the block pass argument evaluated not only before 
> the other args but before the receiver seems broken.
> 
> Unlike Ruby 1.8, Ruby 1.9 and JRuby behave the same, with the order 
> being exactly what you'd expect:
> 
> CODE
> obj = Object.new
> def obj.foo(a, b, &c)
>   [a, b, c ? c.call : nil]
> end
> pr = proc {3}
> p ((p 'a'; obj).foo((p 'b'; 1), (p 'c'; 2), &(p 'd'; pr)))"
> Ruby 1.8:
> "d"
> "a"
> "b"
> "c"
> [1, 2, 3]
> 
> Ruby 1.9:
> "a"
> "b"
> "c"
> "d"
> [1, 2, 3]
> 
> JRuby:
> "a"
> "b"
> "c"
> "d"
> [1, 2, 3]
> 
> Rubinius still evaluates arguments in reverse order, and then evaluates 
> block pass after the arguments but before the receiver. I believe this 
> is being "fixed", but at the moment it's the most unexpected behavior of 
> the four:
> 
> "c"
> "b"
> "d"
> "a"
> [1, 2, 3]
> 
> - Charlie
>