digitalmars.D - templating operators
- Brad Roberts (56/56) Mar 02 2006 I'm trying to create a container that will allow arbitrary key/value pai...
- Derek Parnell (28/94) Mar 02 2006 When I did this sort of thing I had to chnage the template name to be
- Brad Roberts (20/52) Mar 02 2006 This works wonderfully for opIndexAssign, but not so much for multiple
- Derek Parnell (12/20) Mar 02 2006 That would because one can't overload the return type. Your code is kind...
I'm trying to create a container that will allow arbitrary key/value pair
trees. Box seems like a great start at supporting a 'holds anything'
container. The next step is making a smooth associative array of them.
However, I don't seem to be able to create a nice templated opIndex or
opIndexAssign.
-------- test.d ---------
import std.stdio;
import std.boxer;
class ValueContainer
{
Box[char[]] _objects;
template opIndex(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
int opIndexAssign(int newValue, char[] key)
{
_objects[key] = box(newValue);
return 0;
}
template getValue(T)
{
T getValue(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
template insertKeyAndValue(T)
{
void insertKeyAndValue(char[] key, T newValue)
{
_objects[key] = box(newValue);
}
}
}
int main()
{
ValueContainer values = new ValueContainer();
values["int"] = 1;
values.insertKeyAndValue!(int)("key", 10);
writef("int: %s\n", values["int"]);
writef("key: %s\n", values["key"]);
writef("key: %s\n", values.getValue!(int)("key"));
return 0;
}
---------------
$ dmd -g test.d
test.d(46): no [] operator overload for type test.ValueContainer
test.d(47): no [] operator overload for type test.ValueContainer
test.d(48): function expected before (), not 0 of type int
Any thoughts on how to make this work well?
Thanks,
Brad
Mar 02 2006
On Thu, 2 Mar 2006 18:01:07 -0800, Brad Roberts wrote:
I'm trying to create a container that will allow arbitrary key/value pair
trees. Box seems like a great start at supporting a 'holds anything'
container. The next step is making a smooth associative array of them.
However, I don't seem to be able to create a nice templated opIndex or
opIndexAssign.
-------- test.d ---------
import std.stdio;
import std.boxer;
class ValueContainer
{
Box[char[]] _objects;
template opIndex(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
int opIndexAssign(int newValue, char[] key)
{
_objects[key] = box(newValue);
return 0;
}
template getValue(T)
{
T getValue(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
template insertKeyAndValue(T)
{
void insertKeyAndValue(char[] key, T newValue)
{
_objects[key] = box(newValue);
}
}
}
int main()
{
ValueContainer values = new ValueContainer();
values["int"] = 1;
values.insertKeyAndValue!(int)("key", 10);
writef("int: %s\n", values["int"]);
writef("key: %s\n", values["key"]);
writef("key: %s\n", values.getValue!(int)("key"));
return 0;
}
---------------
$ dmd -g test.d
test.d(46): no [] operator overload for type test.ValueContainer
test.d(47): no [] operator overload for type test.ValueContainer
test.d(48): function expected before (), not 0 of type int
Any thoughts on how to make this work well?
When I did this sort of thing I had to chnage the template name to be
different to the member inside the template *and* I had to instantiate the
member inside the class. The instantiation didn't surprise me but the
naming conflict one did. Anyhow, replace ...
template opIndex(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
with ...
template opIndex_T(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
alias opIndex_T!(int).opIndex opIndex;
and it should work now.
--
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
3/03/2006 3:14:03 PM
Mar 02 2006
On Fri, 3 Mar 2006, Derek Parnell wrote:
When I did this sort of thing I had to chnage the template name to be
different to the member inside the template *and* I had to instantiate the
member inside the class. The instantiation didn't surprise me but the
naming conflict one did. Anyhow, replace ...
template opIndex(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
with ...
template opIndex_T(T)
{
T opIndex(char[] key)
{
return unbox!(T)(_objects[key]);
}
}
alias opIndex_T!(int).opIndex opIndex;
and it should work now.
--
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
3/03/2006 3:14:03 PM
This works wonderfully for opIndexAssign, but not so much for multiple
types of aliases for opIndex.
alias opIndex_T!(int).opIndex opIndex;
alias opIndex_T!(float).opIndex opIndex;
test.d(54): function alias opIndex called with argument types:
(char[3])
matches both:
test.ValueContainer.opIndex_T!(int).opIndex(char[])
and:
test.ValueContainer.opIndex_T!(float).opIndex(char[])
test.d(55): function alias opIndex called with argument types:
(char[3])
matches both:
test.ValueContainer.opIndex_T!(int).opIndex(char[])
and:
test.ValueContainer.opIndex_T!(float).opIndex(char[])
test.d(56): function expected before (), not 0 of type int
So close...
Brad
Mar 02 2006
Derek Parnell <derek psych.ward>
On Thu, 2 Mar 2006 21:38:09 -0800, Brad Roberts wrote:
On Fri, 3 Mar 2006, Derek Parnell wrote:
This works wonderfully for opIndexAssign, but not so much for multiple
types of aliases for opIndex.
alias opIndex_T!(int).opIndex opIndex;
alias opIndex_T!(float).opIndex opIndex;
That would because one can't overload the return type. Your code is kinda
like doing ...
int opIndex(char[] x) ...
float opIndex(char[] x) ...
and that just ain't going to fly.
--
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
3/03/2006 4:45:56 PM
Mar 02 2006