Don't write unintentionally non-generic code

Reason

Generality. Reusability. Don't gratuitously commit to details; use the most general facilities available.

Example

Use != instead of < to compare iterators; != works for more objects because it doesn't rely on ordering.

for (auto i = first; i < last; ++i) {   // less generic
    // ...
}

for (auto i = first; i != last; ++i) {   // good; more generic
    // ...
}

Of course, range-for is better still where it does what you want.

Example

Use the least-derived class that has the functionality you need.

class Base {
public:
    Bar f();
    Bar g();
};

class Derived1 : public Base {
public:
    Bar h();
};

class Derived2 : public Base {
public:
    Bar j();
};

// bad, unless there is a specific reason for limiting to Derived1 objects only
void my_func(Derived1& param)
{
    use(param.f());
    use(param.g());
}

// good, uses only Base interface so only commit to that
void my_func(Base& param)
{
    use(param.f());
    use(param.g());
}

Enforcement

• Flag comparison of iterators using < instead of !=.
• Flag x.size() == 0 when x.empty() or x.is_empty() is available. Emptiness works for more containers than size(), because some containers don't know their size or are conceptually of unbounded size.
• Flag functions that take a pointer or reference to a more-derived type but only use functions declared in a base type.