What are the roles of template libraries and generic libraries in C++ generic programming?

Template libraries and generic libraries implement generic programming by allowing data type parameterization and providing predefined templates, improving code reusability and flexibility, including: Template library: providing a template declaration mechanism, creating A type or function parameterized based on a data type, such as a std::vector template container. Generic library: Provides predefined template functions and types that perform common tasks, such as the std::sort generic function for sorting elements.

The role of template libraries and generic libraries in C generic programming

Overview

Generic programming in C allows the development of code that works for a variety of data types, improving code reusability and flexibility. Template libraries and generic libraries are key components for implementing generic programming.

Template library

The template library provides a mechanism for declaring templates, allowing you to create parameterized types or functions based on data types. For example, std::vector is a template container that accepts a type parameter to store elements.

Code sample:

#include <vector>

// 定义存储整数的模板向量
template <typename T>
using IntVector = std::vector<T>;

// 创建一个存储整数的向量
IntVector<int> myVector;
myVector.push_back(10);

Generic library

The generic library provides predefined template functions and types that are available for performing a variety of common tasks. For example, std::sort is a generic function that accepts a comparison function to sort elements.

Code example:

#include <algorithm>

// 比较函数
int compare(const int& a, const int& b) {
  return a > b;
}

// 对向量进行降序排序
std::sort(myVector.begin(), myVector.end(), compare);

Practical case

Consider the following matrix multiplication problem:

A = [[1, 2], [3, 4]]
B = [[5, 6], [7, 8]]
C = A * B = [[19, 22], [43, 50]]

Using generic programming, we can create a template function to perform matrix multiplication that will work for any element type.

#include <vector>

// 矩阵相乘模板函数
template <typename T>
std::vector<std::vector<T>> matrixMultiply(const std::vector<std::vector<T>>& a, const std::vector<std::vector<T>>& b) {
  int m = a.size(), n = a[0].size(), p = b[0].size();
  std::vector<std::vector<T>> c(m, std::vector<T>(p, 0));

  for (int i = 0; i < m; i++) {
    for (int j = 0; j < p; j++) {
      for (int k = 0; k < n; k++) {
        c[i][j] += a[i][k] * b[k][j];
      }
    }
  }

  return c;
}

// 矩阵相乘实战
auto c = matrixMultiply(a, b);

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