I’ve pulled and pushed to a common branch that only existed on the machines of a colleague and mine to avoid running automatic pipelines due to us pushing to the gitlab remote, since we were doing some experimentation. I’ve also pulled and pushed from a separate repo on my own machine.

Git is fantastic, because these use cases are not edge cases but standard

Still more readable than APL

Meh. Been developing professionally with C++ for 10 years at this point. I’m one of the weird people that kinda likes C++ and its pragmatism despite all its warts.

I’d like C++ better if it didn’t have inheritance. There are better solutions to model interfaces, and without inheritance people can’t write class hierarchies that are 10 levels deep with a different set of virtual functions overridden (and new virtual functions added) at each level.

And yes, that is not hypothetical. Real codebases in the real world shipping working products do that, and it’s about as nice as you can imagine.

You do have a terminology mismatch. In C++, an abstract class is a class with at least one pure virtual method.

Such classes cannot be instantiated, so they are useful only as base classes.

An interface is more of a concept than a thing.

Sure you can say that Iterable is an interface that provides the Next() and Prev() methods and you can say that Array is an Iterable because it inherits from Iterable (and then you override those methods to do the correct thing), and that’s one way to implement an interface in C++.

But you can also say that Iterable<T> is a class template that provides a Next() and Prev() methods that call the methods of the same name on the type that they wrap (CRTP aka static polymorphism).

Or you can say that an algorithm that scans a collection T forward requires the collection to have a Next() method by calling Next() on it.

And I can think of at least 2 other ways to define an interface that isn’t using abstract classes.

And even if using abstract classes, inheriting from them is definitely the least flexible way to use them to define an interface, because it doesn’t allow one to do something like mocking functionality in tests, because it’s not possible to redefine the class to be tested to inherit from the test interface implementation with mocked functionality, so one still needs something to the effect of dependency injection anyway.

So yeah, abstract class is very different from inheritance, and it’s also very different from interface, even though it relates to both.

I thought mint was switching to a debian base but it looks like I am mistaken. While LMDE exists, it’s still not the default.

Got the feeling that’s probably gonna change soonish, we’ll see.

Since my previous example didn’t really have return value, I am changing it slightly. So if I’m reading your suggestion of “rewriting that in 3 lines and a single nested scope followed by a single return”, I think you mean it like this?

int retval = 0;

// precondition checks:
if (!p1) retval = -ERROR1;
if (p2) retval = -ERROR2;
if (!p3 && p4) retval = -ERROR3;

// business logic:
if (p1 && !p2 && (p3 || !p4))
{
    retval = 42;
}

// or perhaps would you prefer the business logic check be like this?
if (retval != -ERROR1 && retval != -ERROR2 && retval != -ERROR3)
{
    retval = 42;
}

// or perhaps you'd split the business logic predicate like this? (Assuming the predicates only have a value of 0 or 1)
int ok = p1;
ok &= !p2;
ok &= p3 || !p4;
if (ok)
{
    retval = 42;
}

return retval;

as opposed to this?

// precondition checks:
if(!p1) return -ERROR1;
if(p2) return -ERROR2;
if(!p3 && p4) return -ERROR3;

// business logic:
return 42;

Using a retval has the exact problem that you want to avoid: at the point where we do return retval, we have no idea how retval was manipulated, or if it was set multiple times by different branches. It’s mutable state inside the function, so any line from when the variable is defined to when return retval is hit must now be examined to know why retval has the value that it has.

Not to mention that the business logic then needs to be guarded with some predicate, because we can’t early return. And if you need to add another precondition check, you need to add another (but inverted) predicate to the business logic check.

You also mentioned resource leaks, and I find that a more compelling argument for having only a single return. Readability and understandability (both of which directly correlate to maintainability) are undeniably better with early returns. But if you hit an early return after you have allocated resources, you have a resource leak.

Still, there are better solutions to the resource leak problem than to clobber your functions into an unreadable mess. Here’s a couple options I can think of.

1. Don’t: allow early returns only before allocating resources via a code standard. Allows many of the benfits of early returns, but could be confusing due to using both early returns and a retval in the business logic
2. If your language supports it, use RAII
3. If your language supports it, use defer
4. You can always write a cleanup function

Example of option 1

// precondition checks
if(!p1) return -ERROR1;
if(p2) return -ERROR2;
if(!p3 && p4) return -ERROR3;

void* pResource = allocResource();
int retval = 0;

// ...
// some business logic, no return allowed
// ...

freeResource(pResource);
return retval; // no leaks

Example of option 2

// same precondition checks with early returns, won't repeat them for brevity

auto Resource = allocResource();

// ...
// some business logic, return allowed, the destructor of Resource will be called when it goes out of scope, freeing the resources. No leaks
// ...

return 42;

Example of option 3

// precondition checks

void* pResource = allocResource();
defer freeResource(pResource);

// ...
// some business logic, return allowed, deferred statements will be executed before return. No leaks
// ...

return 42;

Example of option 4

int freeAndReturn(void* pResource, const int retval)
{
    freeResource(pResource);
    return retval;
}

int doWork()
{
    // precondition checks

    void* pResource = allocResource();

    // ...
    // some business logic, return allowed only in the same form as the following line
    // ...

    return freeAndReturn(pResource, 42);
}

Bad advice. Early return is way easier to parse and comprehend.

if (p1)
{
    if(!p2)
    {
        if(p3 || !p4)
        {
            *pOut = 10;
        }
    }
}

vs

if(!p1) return;
if(p2) return;
if(!p3 && p4) return;

*pOut = 10;

Early out makes the error conditions explicit, which is what one is interested in 90% of the time. After the last if you know that all of the above conditions are false, so you don’t need to keep them in your head.

And this is just a silly example with 3 predicates, imagine how a full function with lots of state looks. You would need to keep the entire decision tree in your head at all times. That’s the opposite of maintainable.

If this was cpp, clang-tidy would tell you “do not use else after return”

I don’t know how null works in swift, but assuming it coerces to bool I’d write

if (a) return a;
return b;