For any independent variable x 1, x2 in the domain of function f(x), when X 1

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Function is a basic concept in mathematics and computer science. It is a relationship or mapping that maps input values to output values. Mathematically, a function can be regarded as a rule or algorithm for calculating an output value according to a given input value. In computer science, a function is a block of program code, which is used to perform a specific task and can accept input parameters and return results.

A unique identifier used to identify the function, which is convenient for subsequent reference and use. Used to define the input value accepted by the function, which can be zero or more. The result returned by the function can be any type of data, such as integer, floating point number, string, array and so on. Contains the program code block to realize the function, which is the main part of the function.

There are many classification methods of functions, such as trigonometric function, exponential function, logarithmic function and so on. Functions used in computer programs are defined according to specific business logic and application scenarios, such as sorting function, calculation function, query function, etc.

Call your own function in the function definition to solve the problem that you need to perform the same or similar tasks repeatedly. A function used to calculate a set of values, such as sum, maximum, average, etc. A user-defined function used to implement a specific function or business logic.

In different programming languages, the definition and implementation of functions may be different, but their core concepts and functions are similar. When defining a function, we need to consider the input parameters, output types, algorithm implementation and return results of the function to ensure the correctness and maintainability of the function.

At the same time, the performance and efficiency of the function need to be considered to ensure that the function can be executed quickly and return the correct results. In the field of computer science, functions have become an important tool for writing high-quality, maintainable and reusable codes.