语法分析实验

一、实验目的及内容实现下述我们定义的语言的语法分析器这种语言的程序结构很简单，语法相当于c的函数体，即由一对大括号括起来的语句序列，没有过程或函数。

声明语句、表达式语句及控制语句的写法都与c 类似，但规定：一条声明语句只能声明一个整型变量，没有数组；控制语句只是if、for和while三个语句，这三个语句本身也可以包含语句序列；表达式仅局限于布尔表达式和整型算术表达式，布尔表达式由对两个算术表达式的比较组成，该比较使用<,>,<=,>=,= =,!=比较运算符；算术表达式可以包括整型常数、变量以及+,－,*,/这四个运算符。

另外，还可以有复合语句。

用read和write语句实现输入输出。

注释用/*和*/括起来，但注释不能嵌套。

二、实验原理及基本技术路线图（方框原理图或程序流程图）实验所用的产生式：<程序> →‘{’ <声明序列> <语句序列> ‘}’<声明序列> → <声明语句> { <声明语句> }<声明语句> → int <标志符>;<语句序列> → <语句> { <语句> }<语句> → <if语句> | <while语句> | <for语句> | <read语句> | <write 语句> | <复合语句> | <表达式语句><if语句> → if (<表达式>) <语句> [ else <语句> ]<while语句> → while (<表达式>) <语句><for语句> → for (<表达式>;<表达式>;<表达式>) <语句><read语句> → read <标识符>;<write语句> → write <表达式>;<复合语句> →‘{ ’ <语句序列>‘ }’<表达式语句> → <表达式>; | ;<表达式> → <布尔表达式> | <标志符> = <布尔表达式><布尔表达式> → <算术表达式> | <算术表达式> ( > | < | >= | <= | == | !=)<算术表达式><算术表达式> → <项> { ( + | - ) <项> }<项> → <因子> { ( * | / ) <因子> }<因子> → (<算术表达式>) | <标识符> | <无符号整数>实验中自定义的函数：int parse();语法分析主函数int program();<程序>int statement();<语句>int expression_stat();<表达式语句>int expression();<表达式>int bool_expr();<布尔表达式>int additive_expr();<算术表达式>int term();<项>int factor();<因子>int if_stat();<if语句>int while_stat();<while语句>int for_stat();<for语句>int write_stat();<write语句>int read_stat();<read语句>int declaration_stat();<声明语句>int declaration_list();<声明序列>int statement_list();<语句序列>int compound_stat();<复合语句>三、所用仪器、材料（设备名称、型号、规格等或使用软件）开发环境/平台：vc++6.0实验器材：兼容计算机一台四、实验方法、步骤（或：程序代码或操作过程）实验源代码：#include <stdio.h>#include <ctype.h>#include <conio.h>#include <string.h>int parse();int program();int statement();int expression_stat();int expression();int bool_expr();int additive_expr();int term();int factor();int if_stat();int while_stat();int for_stat();int write_stat();int read_stat();int declaration_stat();int declaration_list();int statement_list();int compound_stat();char token[20],token1[40];//token保存单词符号，token1保存单词值char Scanout[300]; //保存词法分析输出文件名long count=0;FILE *fp; //用于指向输入输出文件的指针void main(){strcpy(Scanout,"输出.txt");parse();}//语法分析程序int parse(){int es=0;if((fp=fopen(Scanout,"r"))==NULL){printf("\n打开%s错误!\n",Scanout);es=10;}if (es==0) es=program();printf("=====语法分析结果!======\n");switch(es){case 0: printf("语法分析成功!\n");break;case 10: printf("打开文件 %s失败!\n",Scanout);break;case 1: printf("缺少{!\n");break;case 2: printf("缺少}!\n");break;case 3: printf("缺少标识符!\n");break;case 4: printf("少分号!\n");break;case 5: printf("缺少(!\n");break;case 6: printf("缺少)!\n");break;case 7: printf("缺少操作数!\n");break;case 8: printf("缺少运算符!\n");break;}fclose(fp);return(es);}void get(){fscanf(fp,"%s %s\n",&token,&token1);printf("%s %s\n",token,token1);count++;}void back(int j)//文件指针回退一位{int i;printf("文件指针回退%d位!\n",j);rewind(fp);for(i=0;i<count;i++){fscanf(fp,"%s %s\n",&token,&token1);}}//<程序>::={<声明序列><语句序列>}//program::= '{'<declaration_list><statement_list> '}' int program(){int es=0;get();if(strcmp(token,"{"))//判断是否'{'{es=1;return(es);}es=declaration_list();if (es>0) return(es);es=statement_list();if (es>0) return(es);if(strcmp(token,"}"))//判断是否'}'{es=2;return(es);}return(es);}//<声明序列>::=<声明序列><声明语句>|<声明语句>//<declaration_list>::=//<declaration_list><declaration_stat>|<declaration_stat> //改成<declaration_list>::={<declaration_stat>}int declaration_list(){int es=0;get();while (strcmp(token,"int")==0){es=declaration_stat();if (es>0) return(es);}return(es);//<声明语句> ::=int <变量>；//<declaration_stat>::=int ID;int declaration_stat(){int es=0;get();if (strcmp(token,"ID")) return(es=3); //不是标识符get();if (strcmp(token,";") ) return(es=4);get();return(es);}//<语句序列>::=<语句序列><语句>|<语句>//<statement_list>::=<statement_list><statement>|<statement>//改成<statement_list>::={<statement>}int statement_list(){int es=0;while(strcmp(token,"(")==0||strcmp(token,"NUM")==0||strcmp(token,"ID")==0||s trcmp(token,"if")==0||strcmp(token,"while")==0||strcmp(token,"for")==0| |strcmp(token,"read")==0||strcmp(token,"write")==0||strcmp(token,"{")=={es=statement();if (es>0) return(es);get();}return es;}//<语句>::=<if语句>|<while语句>|<for语句>|<read语句> // |<write语句>|<复合语句>|<表达式语句>//<statement>::= <if_stat>|<while_stat>|<for_stat> // |<compound_stat> |<expression_stat>int statement() //error；；；；；；{int es=0;if(strcmp(token,"if")==0){es=if_stat();return es;}if(strcmp(token,"while")==0) {es=while_stat();return es;}if(strcmp(token,"for")==0) {es=for_stat();return es;}if(strcmp(token,"read")==0) {es=read_stat();return es;}if(strcmp(token,"write")==0) {es=write_stat();return es;}if(strcmp(token,"{")==0){es=compound_stat();return es;}else{es=expression_stat();return es;}return es;}//<IF 语句>::= if (<表达式>) <语句 > [else <语句 >]//<IF_stat>::= if (<expr>) <statement > [else < statement >]int if_stat(){int es=0;int temp=0;get();if(strcmp(token,"(")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);get();if(strcmp(token,")")==0){get();es=statement();temp=es;if(es>0) return es;get();if(strcmp(token,"else")==0){ get();es=statement(); }else{count-=1;back(1);es=temp;}//需要做回退操作}else{es=6;return es;}}elsees=5;return es;}//<while语句>::=while(<表达式>) <语句>//<while_stat>::= while (<expr >) < statement > int while_stat(){int es=0;get();if(strcmp(token,"(")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);get();if(strcmp(token,")")==0){get();es=statement();return es;}}else{es=5;return es;}return es;}//<for语句>::=for(<表达式>;<表达式>;<表达式>) <语句 >//<for_stat>::= for(<expr>,<expr>,<expr>)<statement>int for_stat(){int es=0;get();if(strcmp(token,"(")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();if(es>0) return es;}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);get();if(strcmp(token,";")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();if(es>0) return es;}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);get();if(strcmp(token,";")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();if(es>0) return es;}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);get();if(strcmp(token,")")==0){get();es=statement();return es;}else{es=6;return es;}}else{es=4;return es;}}else{es=4;return es;}}else{es=5;return es;}return es;}//<write_语句>::=write <表达式>;//<write_stat>::=write <expression>;int write_stat(){int es=0;get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();if(es>0) return es;get();if(strcmp(token,";")) return 4;}elseif(strcmp(token,"ID"))return (es=3);elseif(strcmp(token,"NUM"))return (es=7);return es;}//<read_语句>::=read <变量>;//<read_stat>::=read ID;int read_stat(){int es=0;get();if (strcmp(token,"ID"))return(es=3); //不是标识符get();if(strcmp(token,";")) return 4;return es;}//<复合语句>::={<语句序列>}//<compound_stat>::= '{'<statement_list> '}' int compound_stat(){ //复合语句函数int es=0;get();es=statement_list();if(es>0) return es;if(strcmp(token,"}")) return (es=2);return es;}//<表达式语句>::=<表达式>;|;//<expression_stat>::=<expression>;|;int expression_stat(){int es=0;if(strcmp(token,";")==0) return es;else{if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0){es=expression();if(es>0) return es;}get();if(strcmp(token,";")) return 4;}return es;}//<表达式>::=<标识符>=<布尔表达式>|<布尔表达式>//<expr>::=ID=<bool_expr>|<bool_expr>int expression(){int es=0;if(strcmp(token,"ID")==0){get();if(strcmp(token,"=")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=bool_expr();if(es>0) return es;}else{count-=2;back(2);get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=bool_expr();}}return es;}//<布尔表达式>::=<算术表达式>|<算术表达式>(>|<|>=|<=|==|!=)<算术表达式> //<bool_expr>::=<additive_expr>// |< additive_expr >(>|<|>=|<=|==|!=)< additive_expr >int bool_expr(){int es=0;es=additive_expr();if(es>0) return es;get();if(strcmp(token,">")==0||strcmp(token,"<")==0||strcmp(token,">=")==0||s trcmp(token,"<=")==0||strcmp(token,"==")==0||strcmp(token,"!=")==0) {get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=additive_expr();if(es>0) return es;}else //keystep{count--;back(1);}return es;}//<算术表达式>::=<项>{(+|-)<项>}//<additive_expr>::=<term>{(+|-)< term >}int additive_expr(){int es=0;es=term();if(es>0) return es;get();if(strcmp(token,"+")==0||strcmp(token,"-")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=term();if(es>0) return es;}else //keystep{count--;back(1);}return es;}//<项>::=<因子>{(*|/)<因子>}//< term >::=<factor>{(*| /)< factor >}int term(){int es=0;es=factor();if(es>0) return es;get();if(strcmp(token,"*")==0||strcmp(token,"/")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=factor();if(es>0) return es;}else //keystep{count--;back(1);}return es;}//<因子>::=(<算术表达式>)|<标识符>|<无符号整数>//< factor >::=(<additive_expr>)| ID|NUMint factor(){int es=0;if(strcmp(token,"(")==0){get();if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")= =0)es=additive_expr();if(es>0) return es;get();if(strcmp(token,")")) return 6;goto a;}elseif(strcmp(token,"ID")==0) goto a;else es=3;if(strcmp(token,"NUM") && es!=0) return(es=7);else es=0;a:return es;}五、实验过程原始记录( 测试数据、图表、计算等)二元组信息运行结果截图：六、实验结果、分析和结论（误差分析与数据处理、成果总结等。