Re: use of struct vs class

[mark via Digitalmars-d-learn]

On Saturday, 7 March 2020 at 10:30:06 UTC, drug wrote:
07.03.2020 13:20, mark пишет:
I have this struct (with details omitted
[ snip ]
Should Deb be a class rather than a struct?

Do you consider using pointers in AA:
```
Deb*[string] debForName;
```

I've done some changes including using Deb* as you suggested:

struct Deb {
    string name;
    ...
    RedBlackTree!string tags;

    bool valid() { return !(name.empty || description.empty); }

    size_t toHash() const @safe nothrow {
        return typeid(name).getHash(&name); // names are unique
    }

    bool opEquals(const Deb other) const @safe pure nothrow {
        return name == other.name; // names are unique
    }

    int opCmp(ref const Deb other) const {
        return cmp(name, other.name); // names are unique
    }
}

Which I now want to store in:

RedBlackTree!Deb* debs; // name-ordered list of deb packages

And now I'm populating like this:

Deb* deb;
auto file = File(filename);
foreach(line; file.byLine) {
    line = strip(line);
    if (line.empty) {
        if (deb != null && deb.valid) {
            debs.insert(deb);
            deb.clear;
        }
        // else report incomplete package
        continue;
    }
    if (deb == null)
        deb = new Deb;
    ...
}
if (deb != null && deb.valid)
    debs.insert(deb);

But it crashes with:

Performing "debug" build using 
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/ldc2 for x86_64.
gtk-d:gtkd 3.9.0: target for configuration "library" is up to 
date.
debfind ~master: building configuration "application"...
src/model.d(96,36): Error: template 
std.container.rbtree.RedBlackTree!(Deb, "a < b", 
false).RedBlackTree.stableInsert cannot deduce function from 
argument types !()(Deb*), candidates are:
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/container/rbtree.d(1256,12):
        stableInsert(Stuff)(Stuff stuff)
  with Stuff = Deb*
  must satisfy the following constraint:
       isImplicitlyConvertible!(Stuff, Elem)
...