Tiny语言编译器开发之词法分析

最新推荐文章于 2025-04-08 11:14:46 发布

hexiaomin_1984

最新推荐文章于 2025-04-08 11:14:46 发布

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本文详细解析了Tiny语言编写的样例程序，通过词法分析过程，逐行解析并标记程序的关键字、标识符及数字，展示了如何使用DFA进行词法分析，最终实现对程序源代码的正确理解与执行。

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对于Tiny语言编写的Sample程序源代码如下：

{ Sample program
in TINY language -
computes factorial
}
read x; { input an integer }
if 0 < x then { don't compute if x <= 0 }
fact := 1;
repeat
fact := fact * x;
x := x - 1
until x = 0;
write fact { output factorial of x }
end

词法分析采用手工构造DFA的方式进行，词法分析主要为后面的各个阶段提供方法getToken;

经过词法分析后每行的关键字、标识符以及数字如下：

   1: { Sample program
   2:   in TINY language -
   3:   computes factorial
   4: }
   5: read x; { input an integer }
        5: reserved word: read
        5: ID, name=x
        5: ;
   6: if 0 < x then { don't compute if x <= 0 }
        6: reserved word: if
        6: NUM, val= 0
        6: <
        6: ID, name=x
        6: reserved word: then
   7:   fact := 1;
        7: ID, name=fact
        7: :=
        7: NUM, val= 1
        7: ;
   8:   repeat
        8: reserved word: repeat
   9:     fact := fact * x;
        9: ID, name=fact
        9: :=
        9: ID, name=fact
        9: *
        9: ID, name=x
        9: ;
10:     x := x - 1
        10: ID, name=x
        10: :=
        10: ID, name=x
        10: -
        10: NUM, val= 1
11:   until x = 0;
        11: reserved word: until
        11: ID, name=x
        11: =
        11: NUM, val= 0
        11: ;
12:   write fact { output factorial of x }
        12: reserved word: write
        12: ID, name=fact
13: end
        13: reserved word: end
        14: EOF