Detailed explanation of C++ function library: guide to extension of system functions

The C function library is a collection of predefined functions and objects used to enhance the functionality of C programs. The standard C function library provides input/output, mathematical calculations, string processing, containers, and algorithmic functions. Extended C libraries such as Boost, Qt, Armadillo, and Eigen provide a wider range of capabilities such as advanced algorithms, GUI development, and linear algebra calculations. In a practical case, we show how to use the function library to extend a C program by using the Boost function library to convert a string to lowercase.

C Function Library Detailed Explanation: System Function Expansion Guide

C Function Library is a predefined collection of functions and objects. Can be used to enhance the functionality of C programs. By using function libraries, programmers can access various operations such as input/output, mathematical calculations, and data structures.

Standard C function library

The C standard library provides the following functions:

• Input/Output (I/O) : used to read and write data.
• Mathematical calculations: including trigonometric, logarithmic and exponential functions.
• String processing: Used to operate strings, such as comparison, search and replacement.
• Container: Used to store and manage data collections.
• Algorithm: Used to sort, search and traverse data.

Extended C function library

In addition to the standard C function library, there are many third-party C function libraries available, which provide a wider range of function. These libraries include:

• Boost Library: Provides high-level algorithms, data structures, and utilities.
• Qt Library: For graphical user interface (GUI) development.
• Armadillo library: for linear algebra calculations.
• Eigen library: used for matrix operations.

Practical case

The following is a practical case using the Boost function library to demonstrate how to use the function library to extend a C program:

#include <iostream>
#include <boost/algorithm/string.hpp>

int main() {
  std::string str = "Hello, world!";

  // 将字符串转换为小写
  boost::algorithm::to_lower(str);

  // 输出转换后的字符串
  std::cout << str << std::endl;

  return 0;
}

In the above example, we included the string algorithm header file of the Boost library. We then use the to_lower() function to convert the string to lowercase. This function is part of the Boost library and is not in the standard C library.

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