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GoPlayWithCompiler
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编译原理之美-宫文学 golang实现版本
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编译原理之美-宫文学-学习摘要 [TOC] # 实现一门脚本语言.原理篇 ## 语法分析（一）：纯手工打造公式计算器 主要是 语法分析的原理和递归下降算法，上下文无关文法。 本课稍有单独，需要看原文。 [作者源码](https://github.com/RichardGong/PlayWithCompiler/blob/master/lab/craft/SimpleCalculator.java) 自己手动实现一遍有助于理解。 ## 语法分析（二）：解决二元表达式中的难点 巴科斯范式 BNF ``` add ::= mul | add + mul ``` 扩展巴科斯范式 EBNF ``` add -> mul ( + mul ) * ``` 一个规律： >对于左结合的运算符，递归项要放在左边；而右结合的运算符，递归项放在右边。 但是左递归有个无限循环的问题。 解决办法是修改文法： ``` add -> mul add' add' -> + mul add' | ε ``` 可以用EBNF表达为 ``` add -> mul ( + mul ) * ``` ## 语法分析(三)：实现一门简单的脚本语言 就是进一步扩展代码 ## 编译器前端工具（二）：用Antlr生成词法、语法分析器 [antlr官网](https://www.antlr.org/) mac 可以直接用homebrew 安装。 [antlr语法参考](https://github.com/antlr/grammars-v4) ### 词法分析 antlr规则文件以`.g4`结尾。 示例 Hello.g4 ``` lexer grammar Hello; //lexer 关键字意味着这是一个词法规则文件，名称是 Hello，要与文件名相同 // 关键字 If : 'if'; Int : 'int'; // 字面量 IntLiteral: [0-9]+; StringLiteral: '"' .*? '"' ; // 字符串字面量 // 操作符 AssignmentOP: '=' ; RelationalOP: '>'|'>='|'<' |'<=' ; Star: '*'; Plus: '+'; Sharp: '#'; SemiColon: ';'; Dot: '.'; Comm: ','; LeftBracket : '['; RightBracket: ']'; LeftBrace: '{'; RightBrace: '}'; LeftParen: '('; RightParen: ')'; // 标识符 Id : [a-zA-Z_] ([a-zA-Z_] | [0-9])*; // 空白字符，抛弃 Whitespace: [ \t]+ -> skip; Newline: ( '\r' '\n'?|'\n')-> skip; ``` 生成golang的需要[参考](https://github.com/antlr/antlr4/blob/master/doc/go-target.md) `go get github.com/antlr/antlr4/runtime/Go/antlr` **编译词法规则** ``` antlr -Dlanguage=Go Hello.g4 ``` 生成了3个文件`Hello.interp` `Hello.tokens` `hello_lexer.go` 手写一个grun.go ``` package main import ( parser "GoPlayWithCompiler/antlrdemo" "fmt" "github.com/antlr/antlr4/runtime/Go/antlr" "os" ) func main() { input, _ := antlr.NewFileStream(os.Args[1]) lexer := parser.NewHello(input) stream := antlr.NewCommonTokenStream(lexer, 0) stream.Fill() for _, token := range stream.GetAllTokens() { fmt.Println(token) } } ``` 执行以下命令获取token: `go run cmds/hello/main.go antlrdemo/Hello/hello.play` 生成如下文本： ``` [@0,0:2='int',<2>,1:0] [@1,4:6='age',<19>,1:4] [@2,8:8='=',<5>,1:8] [@3,10:11='45',<3>,1:10] [@4,12:12=';',<10>,1:12] [@5,14:15='if',<1>,2:0] [@6,17:17='(',<17>,2:3] [@7,18:20='age',<19>,2:4] [@8,22:23='>=',<6>,2:8] [@9,25:26='17',<3>,2:11] [@10,27:27='+',<8>,2:13] [@11,28:28='8',<3>,2:14] [@12,29:29='+',<8>,2:15] [@13,30:31='20',<3>,2:16] [@14,32:32=')',<18>,2:18] [@15,33:33='{',<15>,2:19] [@16,37:42='printf',<19>,3:2] [@17,43:43='(',<17>,3:8] [@18,44:59='"Hello old man!"',<4>,3:9] [@19,60:60=')',<18>,3:25] [@20,61:61=';',<10>,3:26] [@21,63:63='}',<16>,4:0] [@22,64:63='<EOF>',<-1>,4:1] ``` ### 语法分析 `PlayScript.g4` ``` grammar PlayScript; import CommonLexer; // 导入词法定义 /* 下面的内容加到所生成的 Java 源文件的头部，如包名称，import 语句等。*/ @header { package antlrtest; } expression : assignmentExpression | expression ',' assignmentExpression ; assignmentExpression : additiveExpression | Identifier assignmentOperator additiveExpression ; assignmentOperator : '=' | '*=' | '/=' | '%=' | '+=' | '-=' ; additiveExpression : multiplicativeExpression | additiveExpression '+' multiplicativeExpression | additiveExpression '-' multiplicativeExpression ; multiplicativeExpression : primaryExpression | multiplicativeExpression '*' primaryExpression | multiplicativeExpression '/' primaryExpression | multiplicativeExpression '%' primaryExpression ; ``` 生成目标文件`antlr -Dlanguage=Go PlayScript.g4` 手写个交互式脚本来解析语法，并画出ast树。具体[参考](https://github.com/bjmayor/GoPlayWithCompiler/blob/master/cmds/playScript/main.go) [json](https://github.com/antlr/grammars-v4/blob/master/json/JSON.g4)的这个语法很简单，适合学习。
