詞法分析器

詞法分析器用來給語法分析器提供token，每個token都有乙個屬性tokentype用來指明其類別。

public enum tokentype

public class token
public token(tokentype type)
=> this.type = type;
public override string tostring()
=> $"";
}

public class integer : token

public integer(int value) : base(tokentype.integer)
=> this.value = value;
public override string tostring()
=> $"integer\t";;
}public class char : token
public char(char value) : base(tokentype.char)
=> this.value = value;
public override string tostring()
=> $"char\t";
}

public class type : word

// width is used for storage allocation
public type(tokentype type, string lexeme, int width) : base(type, lexeme)
=> this.width = width;
}public class word : token
public word(tokentype type, string lexeme) : base(type)
=> this.lexeme = lexeme;
public override string tostring()
=> $"\t";
}

public class lexer

private stringreader reader;
private idictionaryreserveds = new dictionary();
public lexer()
private void reserve(word word) => reserveds.add(word.lexeme, word);
public void loadcode(string code)
public token scan()
else if (curchar == '\n') ++linenumber;
else break;
}switch (curchar)
':case ';':
return new word(tokentype.delimiter, curchar.tostring());
case '\'':
var buffer = new stringbuilder();
while (true)
return new char(buffer.tostring()[0]);
}if (char.isdigit(curchar))
return new integer(int.parse(buffer.tostring()));
}else if (char.isletter(curchar))
var str = buffer.tostring();
if (reserveds.containskey(str))
return reserveds[str];
var id = new word(tokentype.id, str);
reserveds.add(str, id);
return id;
}else
return null;
}private bool readchar(char ch)
}

[testmethod]

public void test1()
else
while(true)
";var lexer = new lexer();
lexer.loadcode(code);
while (true)
\t");
}}輸出如下：
line1 primitive char
line1 id ch
line1 assign =
line1 char a
line1 delimiter ;
line2 primitive bool
line2 id test
line2 assign =
line2 false false
line2 delimiter ;
line3 primitive int
line3 id a
line3 assign =
line3 integer 1
line3 delimiter ;
line4 primitive int
line4 id b
line4 assign =
line4 integer 20
line4 delimiter ;
line5 if if
line5 delimiter (
line5 id a
line5 lt <
line5 id b
line5 delimiter )
line6 delimiter 
line9 else else
line10 delimiter 
line13 while while
line13 delimiter (
line13 true true
line13 delimiter )
line14 delimiter

詞法分析器

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詞法分析器

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詞法分析器

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