constexpr in C++ function declarations: giving constant expressions the power

The constexpr keyword in C allows the declaration of constant expression functions that are evaluated at compile time and produce a constant result. This provides the benefits of compile-time evaluation, optimization opportunities, and protection against accidental modifications. The syntax is: constexpr function_name (parameter list). Practical case: constexpr int factorial(int n) { if (n == 0) { return 1; } else { return n * factorial(n - 1); } }

C constexpr in function declarations: giving the power of constant expressions

In C, theconstexprkeyword allows you to declare constant expression functions that are evaluated at compile time and produces constant results. This provides the following benefits:

• Compile-time evaluation:Constant expression functions are evaluated at compile time, eliminating the overhead of runtime calculations.
• Optimization opportunities:The compiler can optimize constant expression functions because it knows they will be executed at compile time.
• Prevent accidental modification:The value of a constant expression function cannot be modified at runtime, ensuring data integrity.

Syntax

constexprThe syntax of function declaration is as follows:

constexpr  function_name(参数列表);

Among them:

• is the constant value type returned by the function.
• function_nameis the function name.
• Parameter listis the constant expression parameter accepted by the function.

Practical case

The following is a code example using theconstexprconstant expression function:

constexpr int factorial(int n) { if (n == 0) { return 1; } else { return n * factorial(n - 1); } } int main() { constexpr int result = factorial(5); // 在编译时求值 factorial(5) 并存储在 result 中 std::cout << "5 的阶乘为：" << result << std::endl; return 0; }

In this example, ## The #factorialfunction is a constant expression function that computes the factorial of a number using a recursive algorithm.mainTheconstrent staticdeclaration in the function allows the result offactorial(5)to be calculated at compile time and stored in aresultconstant middle.

The parameters and return value of the constant expression function must be constant expressions.
• Constant expression functions cannot call non-
• constfunctions.
Constant expression functions can call other constant expression functions.

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