笔记 - C#从头开始构建编译器 - 1

视频与pr：

作者是 immo landwerth（https://twitter.com/terrajobst），微软 .net 团队的项目经理。

 

这一集主要内容是一个原始的递归下降 parser。

思路：

1.lexer

(1) enum syntaxkind

(2) abstract class syntaxnode

(3) class syntaxtoken : syntaxnode

(4) class lexer

2.expression

(1) abstract class expressionsyntax : syntaxnode

(2) sealed class numberexpressionsyntax : expressionsyntax

(3) sealed class binaryepressionsyntax : expressionsyntax

(4) sealed class parenthesizedexpressionsyntax : expressionsyntax

3.parser

(1) sealed class syntaxtree

(2) class parser

处理优先级的技巧：

public expressionsyntax parseterm()
{
    var left = parsefactor();

    while (current.kind == syntaxkind.plustoken || current.kind == syntaxkind.minustoekn)
    {
        var operatortoken = nexttoken();
        var right = parsefactor();
        left = new binaryepressionsyntax(left, operatortoken, right);
    }

    return left;
}

public expressionsyntax parsefactor()
{
    var left = parseprimaryexpression();

    while (current.kind == syntaxkind.startoken || current.kind == syntaxkind.slashtoken)
    {
        var operatortoken = nexttoken();
        var right = parseprimaryexpression();
        left = new binaryepressionsyntax(left, operatortoken, right);
    }

    return left;
}

4.evaluator

(1) class evaluator

5. 其他

比如诊断信息等

 

c#语言点：

1.public override ienumerable<syntaxnode> getchildren() => enumerable.empty<syntaxnode>();

2.yield