Re: Overriding to!string on enum types
On Tuesday, 2 September 2014 at 12:54:55 UTC, Nordlöw wrote:
Is it possible to override the behaviour of to!string(x) when x
is an enum. I'm asking because this
enum CxxRefQualifier
{
none,
normalRef,
rvalueRef
}
string toString(CxxRefQualifier refQ) @safe pure nothrow
{
final switch (refQ)
{
case CxxRefQualifier.none: return ;
case CxxRefQualifier.normalRef: return ;
case CxxRefQualifier.rvalueRef: return ;
}
}
doesn't affect behaviour of to!string(x) when x is an instance
of CxxRefQualifier.
i can think of two ways(both from memory)
1) specialized template override
template to(T: enum)(T s)
{
string to(T s) { .. your custom code .. }
}
or just stringof
CxxRefQualifier crq = CxxRefQualifier.normalRef;
assert(crq == normalRef);
Re: Overriding to!string on enum types
sorry, i forgot everything.
here is example of how to do this
-
import std.conv : to;
enum Test
{
One,
Two,
Three,
}
template to(T: string)
{
T to(A: Test)(A val)
{
final switch (val)
{
case Test.One: return 1;
case Test.Two: return 2;
case Test.Three: return 3;
}
}
}
void main()
{
assert(to!string(Test.One) == 1);
auto t = cast(Test)2;
assert(to!string(t) == 3);
assert(to!int(4) == 4); // shows original to! template works
}
Re: Overriding to!string on enum types
On Tuesday, 2 September 2014 at 14:59:41 UTC, evilrat wrote:
sorry, i forgot everything.
here is example of how to do this
-
import std.conv : to;
enum Test
{
One,
Two,
Three,
}
template to(T: string)
{
T to(A: Test)(A val)
{
final switch (val)
{
case Test.One: return 1;
case Test.Two: return 2;
case Test.Three: return 3;
}
}
}
void main()
{
assert(to!string(Test.One) == 1);
auto t = cast(Test)2;
assert(to!string(t) == 3);
assert(to!int(4) == 4); // shows original to! template works
}
Word of warning: You are not overriding to, but rather, simply
defining your own to locally, which resolves as a better match
in the context where you are using it.
If you pass the enum to another function in another module, your
to will NOT be called.
Re: Overriding to!string on enum types
On Tuesday, 2 September 2014 at 12:54:55 UTC, Nordlöw wrote:
Is it possible to override the behaviour of to!string(x) when x
is an enum. I'm asking because this
enum CxxRefQualifier
{
none,
normalRef,
rvalueRef
}
string toString(CxxRefQualifier refQ) @safe pure nothrow
{
final switch (refQ)
{
case CxxRefQualifier.none: return ;
case CxxRefQualifier.normalRef: return ;
case CxxRefQualifier.rvalueRef: return ;
}
}
doesn't affect behaviour of to!string(x) when x is an instance
of CxxRefQualifier.
That won't work, because your toString is a free function. The
module system doesn't allow this kind of Koenig lookup-like
hijack. The only reason it allows for things like front/popFront
and arrays, is that the other modules import std.array, and are
aware of the functions. This is not true for user defined
types. This may or may not be a feature :)
Unless we allow defining enum-member functions, AFAIK, it is
impossible to override the printing behavior for enums... short
of injecting your own modules in std.format/std.conv. Or to have
a parameter moduleLookup in said template functions.
Re: Overriding to!string on enum types
On Tuesday, 2 September 2014 at 15:41:17 UTC, monarch_dodra wrote:
Unless we allow defining enum-member functions, AFAIK, it is
impossible to override the printing behavior for enums...
... If your enum actually represents strings, then you could:
enum CxxRefQualifier : string
{
none = ,
normalRef = ,
rvalueRef = ,
}
That in itself is not enough, but you *can* cast your enum to
string, and then print that, or pass that.
See also:
https://issues.dlang.org/show_bug.cgi?id=11571
Re: Overriding to!string on enum types
On Tuesday, 2 September 2014 at 15:42:36 UTC, monarch_dodra wrote: Word of warning: You are not overriding to, but rather, simply defining your own to locally, which resolves as a better match in the context where you are using it. If you pass the enum to another function in another module, your to will NOT be called. i know. and because of that this template in same scope as enum
