How does type deduction for C++ functions work?

C type deduction allows the compiler to automatically infer function parameter and return value types. The syntax is auto func_name(param_list) -> return_type;. The compiler follows the following rules for derivation: 1. Parameter type: initialized parameters are inferred from the expression, and uninitialized parameters default to int; 2. Return value type: the type of the only initialized expression in the function body, or defaults to void. Explicitly specifying types prevents type mismatches and improves readability.

Introduction to type deduction of C functions

Type deduction allows the compiler to infer the parameter type and return value type of a function without explicitly specifying the type. . It simplifies the code and reduces writing boilerplate code.

Syntax

auto func_name(param_list) -> return_type;

• auto Specifies the return type to be inferred.
• param_list is the parameter list of the function. The type can be specified explicitly or deduced using auto.
• return_type is optional to explicitly specify the return value type, otherwise the compiler will infer it.

Practical case

Consider the following function:

// 求两个整数的最大值
auto max(int a, int b) -> int;

The compiler will infer that max the parameter type of the function is an integer, and the return value type is also is an integer.

Automatic deduction rules

The compiler follows the following rules for type deduction:

• For parameter types:

  • if If the parameter is initialized, the type is inferred from the initialization expression.
  • If the parameter is not initialized, the type defaults to int.

• For return value types:

  • If the only expression in the function body is initialized, the type is inferred from that expression.
  • If there is no expression in the function body, the return type defaults to void.

Specify the type explicitly

Sometimes it is preferable to specify the type explicitly rather than using automatic derivation, for example:

// 确保参数和返回值始终为 int
int max(int a, int b) -> int;

This helps To prevent type mismatches and improve code readability.

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