Re: Odd behaviour with multiple return values and varargs

[Eike Decker <eike@...>]

I dislike the truncation of returned arguments also. One way or another, you can
argument for each way how to handle this - however, I would apreciate if lua had
some method to concat multiple return values, just because it can be useful
sometimes, just like the select function can return selected return values. I
always need temporary variables in these cases, and it definitly doesn't look
so nice (but of course, it is more clear in its meaning... ).

It would be more logical in my opinion, that return values are only truncated,
if they are placed in round brackets (just like print((variadic(a,b,c))) will
just print one value).

Eike


> > "Tom Miles" <Tom@creative-assembly.co.uk> writes:
> >
> > > Okay, so I'm obviously missing something with this.  Can anyone
> > > explain the behaviour from this:
> > >
> > > function test1()
> > >     return 1, 2
> > > end
> > >
> > > function test2()
> > >     return 3,4
> > > end
> > >
> > > print(test1(), test2())
> > >
> > >> 1    3    4
> > >
> > > I would have expected it to output 1    2    3    4.  Why doesn't it?
> >
> > Only the last function in a comma list has multiple return values
> > respected.
> 
> On 9/12/07, Tom Miles <Tom@creative-assembly.co.uk> wrote:
> > Is there a good reason for that?  I assume there is, but I'ld like to
> > know, as it seems a bit counter-intuitive.
> 
> At first sight, it's counter-intuitive.
> Think about how you'd write the print() function so that it took
> multiple variadic arguments(??).
> 
> in your example "print(test1(), test2())", if the output was "1 2 3
> 4", from the standpoint of print(), what part of the output is the
> first argument, what part is the rest? How would you write such a
> function in Lua?
> 
> -- count & print the arguments one per line
> function myprint(...)
>    for i,v in pairs({...}) do
>       io.write(i .. ":  " .. v .. "\n")
>    end
> end
> 
> myprint(test1(), test2())
> 1:  1
> 2:  3
> 3:  4
> 
> So, I guess you're hoping the expansion of "print(test1(), test2())"
> would be "print(1,2, 3,4)" but that would be rather difficult to
> handle for anyone writing variadic functions - consider
> 
> 
> function variadic(a, b, ...)
>    print(a, b, ...)
> end
> variadic(test1(), test2())
> 
> What should be in a? what should be in b?
> 
> -K
> 
> PS. Top-posting and HTML-encoded messages are generally accepted as no-noes.
>