On Thursday, 10 May 2018 at 14:15:18 UTC, Yuxuan Shui wrote:
So in D I can use default argument like this:
int f(int line=__LINE__) {}
And because default argument is expanded at call site, f() will
be called with the line number of the call site.
This is a really clever feature, and I think a similar feature
can be useful in other ways.
Say I need to construct a bunch of data structure that takes an
Allocator argument, I need to do this:
...
auto alloc = new SomeAllocator();
auto data1 = new DataStructure(..., alloc);
auto data2 = new DataStructure(..., alloc);
auto data3 = new DataStructure(..., alloc);
...
This looks redundant. But if we have the ability to define more
special keywords like __LINE__, we can do something like this:
...
// constructor of DataStructure
this(Allocator alloc=__ALLOC__) {...}
...
auto alloc = new SomeAllocator();
define __ALLOC__ = alloc;
// And we don't need to pass alloc everytime
...
Is this a good idea?
For things like this you can use the OOP Factory pattern,
pseudocode:
class DataStructureFactory
{
this(Allocator alloc)
{
this.alloc = alloc;
}
Allocator alloc;
DataStructure createDataStructure(...)
{
return new DataStructure(..., alloc)
}
}
DataStructureFactory factory = new DataStructureFactory(new
SomeAllocator())
auto data1 = factory.createDataStructure(...)
auto data2 = factory.createDataStructure(...)
auto data3 = factory.createDataStructure(...)
