C、Java和Python的BNF范式_bnf范式资源-CSDN文库

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BNF范式

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BNF（巴科斯范式，Backus-Naur Form）是一种形式化语法的表示方法，广泛用于描述编程语言的语法结构。它由John Backus和Peter Naur在20世纪50年代末提出，旨在为ALGOL编程语言提供一个清晰的语法定义。在本资源中，我们关注的是C、Java和Python这三种流行的编程语言的BNF范式。让我们详细探讨C语言的BNF范式。C语言的语法严谨且层次分明，它的BNF范式主要涵盖了程序的基本组成部分，如声明（declarations）、表达式（expressions）和控制结构（control structures）。例如，一个简单的C程序可以由一个或多个函数定义组成，每个函数定义包含参数声明、局部变量声明和语句序列。在BNF中，这可能被表示为： ``` <program> ::= <function-definition>+ <function-definition> ::= <declaration-specifiers> <declarator> <compound-statement> <compound-statement> ::= { <declaration>* <statement>* } ``` 接着，我们转向Java。Java作为面向对象的语言，其BNF范式更加复杂，因为它需要描述类、接口、方法、构造函数等概念。例如，Java类定义可能包括类头（class header）和类体（class body）： ``` <class-declaration> ::= <modifiers>? <class-modifiers>? class <identifier> <type-parameters>? <extends-clause>? <implements-clause>? <class-body> <extends-clause> ::= extends <class-type> <implements-clause> ::= implements <interface-type-list> ``` 我们来看Python的BNF范式。Python的语法相对简洁，但仍需涵盖变量定义、表达式、控制流和函数定义等。Python 3.6.1的完整语法规则可以详细描述赋值语句、条件表达式、循环、函数定义等方面。例如，Python的表达式规则可能包括操作符、比较和逻辑表达式： ``` <expression> ::= <or-expression> <or-expression> ::= <and-expression> | <or-expression> "or" <and-expression> <and-expression> ::= <comparison> | <and-expression> "and" <comparison> <comparison> ::= <shift-expression> ( (<comp-op> <shift-expression>)?)* ``` 这些BNF范式是理解语言内部构造的关键，它们帮助开发者和编译器/解释器明确知道合法代码的结构。通过学习这些规则，你可以更深入地了解每种语言的语法特性，从而编写出符合规范的代码。对于教学和语言解析工具的开发来说，BNF范式是必不可少的参考材料。

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Full Grammar specification<a class="headerlink" href="https://elearning.szu.edu.cn/bbcswebdav/pid-394481-dt-content-rid-2786637_1/courses/201820192150306000201/Python%203.6.1%20BNF.htm#full-grammar-specification" title="Permalink to this headline">¶</a></h1> <p>This is the full Python grammar, as it is read by the parser generator and used to parse Python source files:</p> <div class="highlight-python3"><div class="highlight"><pre><span></span><span class="c1"># Grammar for Python</span> <span class="c1"># NOTE WELL: You should also follow all the steps listed at</span> <span class="c1"># https://docs.python.org/devguide/grammar.html</span> <span class="c1"># Start symbols for the grammar:</span> <span class="c1"># single_input is a single interactive statement;</span> <span class="c1"># file_input is a module or sequence of commands read from an input file;</span> <span class="c1"># eval_input is the input for the eval() functions.</span> <span class="c1"># NB: compound_stmt in single_input is followed by extra NEWLINE!</span> <span class="n">single_input</span><span class="p">:</span> <span class="n">NEWLINE</span> <span class="o">|</span> <span class="n">simple_stmt</span> <span class="o">|</span> <span class="n">compound_stmt</span> <span class="n">NEWLINE</span> <span class="n">file_input</span><span class="p">:</span> <span class="p">(</span><span class="n">NEWLINE</span> <span class="o">|</span> <span class="n">stmt</span><span class="p">)</span><span class="o">*</span> <span class="n">ENDMARKER</span> <span class="n">eval_input</span><span class="p">:</span> <span class="n">testlist</span> <span class="n">NEWLINE</span><span class="o">*</span> <span class="n">ENDMARKER</span> <span class="n">decorator</span><span class="p">:</span> <span class="s1">'@'</span> <span class="n">dotted_name</span> <span class="p">[</span> <span class="s1">'('</span> <span class="p">[</span><span class="n">arglist</span><span class="p">]</span> <span class="s1">')'</span> <span class="p">]</span> <span class="n">NEWLINE</span> <span class="n">de

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