sairate
c34823a3bd
- 新增现代 C++ 教程的 Preface 章节，包括英文和中文版本 - 添加 C++ Primer 练习代码 - 新增 Learn C++ 教程的 C++ 开发简介章节 - 添加头文件解析文档 - 更新 mkdocs.yml，包含新教程的目录结构 - 修改项目设置，使用 Python 3.10环境
150 lines
5.8 KiB
Markdown
150 lines
5.8 KiB
Markdown
---
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sort: 1
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---
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# 开始
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## 编写简单的C++程序
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一个函数的定义包含四部分：返回类型、函数名、一个括号包围的形参列表（允许为空）以及函数体。
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## 熟悉编译器
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**g++**：
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- 编译：`g++ 1.1.cpp -o main`
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- 运行：`./main`
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- 查看运行状态：`echo $?`
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- 编译多个文件:`g++ ch2.cpp Sales_item.cc -o main`
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输入 `g++ --help`，查看编译器选项：
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```
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Usage: g++ [options] file...
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Options:
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-pass-exit-codes Exit with highest error code from a phase
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--help Display this information
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--target-help Display target specific command line options
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--help={common|optimizers|params|target|warnings|[^]{joined|separate|undocumented}}[,...]
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Display specific types of command line options
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(Use '-v --help' to display command line options of sub-processes)
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--version Display compiler version information
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-dumpspecs Display all of the built in spec strings
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-dumpversion Display the version of the compiler
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-dumpmachine Display the compiler's target processor
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-print-search-dirs Display the directories in the compiler's search path
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-print-libgcc-file-name Display the name of the compiler's companion library
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-print-file-name=<lib> Display the full path to library <lib>
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-print-prog-name=<prog> Display the full path to compiler component <prog>
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-print-multiarch Display the target's normalized GNU triplet, used as
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a component in the library path
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-print-multi-directory Display the root directory for versions of libgcc
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-print-multi-lib Display the mapping between command line options and
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multiple library search directories
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-print-multi-os-directory Display the relative path to OS libraries
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-print-sysroot Display the target libraries directory
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-print-sysroot-headers-suffix Display the sysroot suffix used to find headers
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-Wa,<options> Pass comma-separated <options> on to the assembler
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-Wp,<options> Pass comma-separated <options> on to the preprocessor
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-Wl,<options> Pass comma-separated <options> on to the linker
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-Xassembler <arg> Pass <arg> on to the assembler
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-Xpreprocessor <arg> Pass <arg> on to the preprocessor
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-Xlinker <arg> Pass <arg> on to the linker
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-save-temps Do not delete intermediate files
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-save-temps=<arg> Do not delete intermediate files
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-no-canonical-prefixes Do not canonicalize paths when building relative
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prefixes to other gcc components
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-pipe Use pipes rather than intermediate files
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-time Time the execution of each subprocess
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-specs=<file> Override built-in specs with the contents of <file>
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-std=<standard> Assume that the input sources are for <standard>
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--sysroot=<directory> Use <directory> as the root directory for headers
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and libraries
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-B <directory> Add <directory> to the compiler's search paths
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-v Display the programs invoked by the compiler
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-### Like -v but options quoted and commands not executed
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-E Preprocess only; do not compile, assemble or link
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-S Compile only; do not assemble or link
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-c Compile and assemble, but do not link
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-o <file> Place the output into <file>
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-pie Create a position independent executable
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-shared Create a shared library
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-x <language> Specify the language of the following input files
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Permissible languages include: c c++ assembler none
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'none' means revert to the default behavior of
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guessing the language based on the file's extension
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```
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输入 `g++ -v --help`可以看到更完整的指令。
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例如还有些常用的：
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```
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-h FILENAME, -soname FILENAME: Set internal name of shared library
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-I PROGRAM, --dynamic-linker PROGRAM: Set PROGRAM as the dynamic linker to use
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-l LIBNAME, --library LIBNAME: Search for library LIBNAME
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-L DIRECTORY, --library-path DIRECTORY: Add DIRECTORY to library search path
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```
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**获得程序状态**:
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- windows: ``echo %ERRORLEVEL%``
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- UNIX: ``echo $?``
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## IO
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- ```#include <iostream>```
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- ```std::cout << "hello"```
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- ```std::cin >> v1```
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记住`>>`和`<<`返回的结果都是左操作数，也就是输入流和输出流本身。
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**endl**：这是一个被称为**操纵符**（manipulator）的特殊值，效果是结束当前行，并将设备关联的缓冲区（buffer）中的内容刷到设备中。
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UNIX和Mac下键盘输入文件结束符：`ctrl+d`，Windows下：`ctrl+z`
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**头文件**：类的类型一般存储在头文件中，标准库的头文件使用`<>`，非标准库的头文件使用`""`。申明写在`.h`文件，定义实现写在`.cpp`文件。
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**避免多次包含同一头文件**：
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```cpp
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#ifndef SALESITEM_H
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#define SALESITEM_H
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// Definition of Sales_itemclass and related functions goes here
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#endif
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```
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**成员函数（类方法）**：使用`.`调用。
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**命名空间（namespace）**：使用作用域运算符`::`调用。
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## 注释
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- 单行注释： `//`
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- 多行注释： `/**/`。编译器将`/*`和`*/`之间的内容都作为注释内容忽略。注意不能嵌套。
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```cpp
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#define SALESITEM_H
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/*
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* 多行注释格式
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* 每一行加一个*
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*/
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```
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## while语句
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循环执行，（直到条件（condition）为假。
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## for语句
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循环头由三部分组成：
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- 一个初始化语句（init-statement）
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- 一个循环条件（condition）
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- 一个表达式（expression）
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## 使用文件重定向
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``./main <infile >outfile``
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