On 02/12/2012 15:09, js.mdnq wrote:
Can this be made to work in D?
Error in D, x not found:
if (auto x = "thing" in arr && x == 45)
{
}
Works:
if (auto x = "thing" in arr)
if (x == 45)
{
}
Most programmers would probably just pollute the existing scope:
auto x = "thing" in arr;
if (x && *x == 45)
{
...
}
I expect this is because wrapping the above in {} for a new scope is
just too ugly, introducing more nesting and indentation.
It would be nice if there was a way of introducing a new scope just for
a declaration and the next statement, something like:
with auto x = "thing" in arr:
if (x && *x == 45)
{
// x is still visible here
}
That would overload 'with' with a different meaning, but would be clear
enough IMO. It would be useful with other constructs like while, do,
foreach, etc. I think it would be more elegant than allowing a
declaration clause in all constructs (like the 'for' statement has). As
you have shown, D's 'if' statement declaration form is perhaps not very
useful.
About while declaration syntax, see:
http://d.puremagic.com/issues/show_bug.cgi?id=5432
