Reason

Shallow nesting of conditions makes the code easier to follow. It also makes the intent clearer. Strive to place the essential code at outermost scope, unless this obscures intent.

Example

Use a guard-clause to take care of exceptional cases and return early.

// Bad: Deep nesting
void foo() {
    ...
    if (x) {
        computeImportantThings(x);
    }
}

// Bad: Still a redundant else.
void foo() {
    ...
    if (!x) {
        return;
    }
    else {
        computeImportantThings(x);
    }
}

// Good: Early return, no redundant else
void foo() {
    ...
    if (!x)
        return;

    computeImportantThings(x);
}

Example

// Bad: Unnecessary nesting of conditions
void foo() {
    ...
    if (x) {
        if (y) {
            computeImportantThings(x);
        }
    }
}

// Good: Merge conditions + return early
void foo() {
    ...
    if (!(x && y))
        return;

    computeImportantThings(x);
}

Enforcement

Flag a redundant else. Flag a function whose body is simply a conditional statement enclosing a block.

C: Classes and class hierarchies

A class is a user-defined type, for which a programmer can define the representation, operations, and interfaces. Class hierarchies are used to organize related classes into hierarchical structures.

Class rule summary:

• C.1: Organize related data into structures (structs or classes)
• C.2: Use class if the class has an invariant; use struct if the data members can vary independently
• C.3: Represent the distinction between an interface and an implementation using a class
• C.4: Make a function a member only if it needs direct access to the representation of a class
• C.5: Place helper functions in the same namespace as the class they support
• C.7: Don't define a class or enum and declare a variable of its type in the same statement
• C.8: Use class rather than struct if any member is non-public
• C.9: Minimize exposure of members

Subsections:

• C.concrete: Concrete types
• C.ctor: Constructors, assignments, and destructors
• C.con: Containers and other resource handles
• C.lambdas: Function objects and lambdas
• C.hier: Class hierarchies (OOP)
• C.over: Overloading and overloaded operators
• C.union: Unions