Re: static opCall not working?
On Sunday, 19 July 2015 at 10:26:04 UTC, TC wrote: What is wrong here? Docs or behavior? Tested it on asm.dlang.org where it fails with all compiler versions. Docs are wrong here. `static opCall` was never intended to be used as constructor and I consider it a bad style in general. This is simply a workaround that people unhappy with lack of default struct constructor used but language actively resists such misusage (`auto s = new S(42)` won't work too btw) and it only causes confusion.
Re: static opCall not working?
On Sunday, 19 July 2015 at 13:25:41 UTC, Ali Çehreli wrote:
On 07/19/2015 03:26 AM, TC wrote:
I tested the code from: http://dlang.org/struct.html
Section: Dynamic Initialization of Structs
struct S
{
int a;
static S opCall(int v)
{
S s;
s.a = v;
return s;
}
static S opCall(S v)
{
S s;
s.a = v.a + 1;
return s;
}
}
S s = 3; // sets s.a to 3
S t = s; // sets t.a to 3, S.opCall(s) is not called
which does not compile (Error: cannot implicitly convert
expression (3)
of type int to S).
What is wrong here? Docs or behavior? Tested it on
asm.dlang.org where
it fails with all compiler versions.
The docs are not clear: s and t are not meant to be
module-scope variables, which should be initialized in a
'static this()' (or 'shared static this()'). Put them inside a
function like main() and it works fine.
I think that's not what the OP means. The documentation is indeed
saying that a struct with static opCall() can be used to
_construct_ the structure, with exactly this syntax, i.e. not
with `S a = S(3);`, but with `S a = 3;`. I, too, find this very
surprising. opCall() is not a constructor...
Re: static opCall not working?
On 07/19/2015 03:26 AM, TC wrote:
I tested the code from: http://dlang.org/struct.html
Section: Dynamic Initialization of Structs
struct S
{
int a;
static S opCall(int v)
{
S s;
s.a = v;
return s;
}
static S opCall(S v)
{
S s;
s.a = v.a + 1;
return s;
}
}
S s = 3; // sets s.a to 3
S t = s; // sets t.a to 3, S.opCall(s) is not called
which does not compile (Error: cannot implicitly convert expression (3)
of type int to S).
What is wrong here? Docs or behavior? Tested it on asm.dlang.org where
it fails with all compiler versions.
The docs are not clear: s and t are not meant to be module-scope
variables, which should be initialized in a 'static this()' (or 'shared
static this()'). Put them inside a function like main() and it works fine.
Ali
static opCall not working?
I tested the code from: http://dlang.org/struct.html
Section: Dynamic Initialization of Structs
struct S
{
int a;
static S opCall(int v)
{
S s;
s.a = v;
return s;
}
static S opCall(S v)
{
S s;
s.a = v.a + 1;
return s;
}
}
S s = 3; // sets s.a to 3
S t = s; // sets t.a to 3, S.opCall(s) is not called
which does not compile (Error: cannot implicitly convert
expression (3) of type int to S).
What is wrong here? Docs or behavior? Tested it on asm.dlang.org
where it fails with all compiler versions.
