The principle of C++ function return value type inference

The function return value type in C is inferred by the compiler. The principle is to analyze the function body through template metaprogramming (TMP), and deduce the type based on the return value of the return statement: Single return statement: The return value is the type of the return expression. Multiple return statements: The return value is the common type of all return expressions. No return statement: the return value type is void. Type inference simplifies code, eliminates type mismatch errors, improves readability and reduces code duplication.

C Principles and practical cases of function return value type inference

In C, the return value type of a function is usually clear declared. However, starting with the C 11 standard, the compiler can infer the return type of a function. This simplifies code writing and eliminates compiler errors due to type mismatches.

The principle of type inference

The C compiler implements type inference using a technique called template metaprogramming (TMP). TMP allows operations on types and templates to be performed at compile time. For return type deduction, the compiler examines the function body and attempts to determine the type of the return value.

Type derivation rules

The compiler follows the following rules to infer the return value type:

• If there is only one return in the function body statement, the return value type is the type of the expression returned in the statement.
• If the function body has multiple return statements, the return value type is the common type of all return expressions.
• If the function body does not have a return statement, the return value type is void.

Practical case

The following example demonstrates how to use function return value type inference:

// 推断返回值类型为 int
int get_number() {
  return 42;
}

// 推断返回值类型为 vector<int>
vector<int> get_numbers() {
  return {1, 2, 3, 4};
}

Benefits

Type inference provides the following benefits:

• Simplified code: there is no need to explicitly declare the return value type.
• Eliminate type mismatch errors: The compiler will detect type mismatches at compile time and report an error.
• Improve code readability: Concise code is easier to read and maintain.
• Reduce code duplication: There is no need to repeatedly specify the return value type in the function header and implementation.

The above is the detailed content of The principle of C++ function return value type inference. For more information, please follow other related articles on the PHP Chinese website!