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[Jonathan M Davis]

On Monday, February 13, 2012 21:49:05 Artur Skawina wrote:
> "argument evaluation" in this context means that given eg "f(a,b,c);"
> it's not specified in what order the expressions 'a', 'b', and 'c'
> are evaluated, which matters if they are dependent or have side
> effects. (depending on arg passing conventions it can make sense to
> implement this one way or the other). If an expression is specced
> as l-t-r (as CatExpression is here) then the call to foo() must
> happen before executing bar(); the operator only comes into play later.

Ideally perhaps, but I expect that that's not true, because operator 
overloading is done via lowering.

foo() ~ bar()

would become

opBinary!"~"(foo(), bar());

which is a normal function call. It's possible that the compiler always 
evaluates foo first, but I'd seriously advise against relying on it.

In the long run, it probably will be guaranteed, because Walter wants to make 
it so that function arguments are always evaluated left-to-right, but until 
that happens, I wouldn't bet on foo() ~ bar() being guaranteed to have foo 
called before bar, even it's supposed to be.

- Jonathan M Davis