語法分析實驗-2

實驗?zāi)康募皟?nèi)容實現(xiàn)下述我們定義的語言的語法分析器這種語言的程序結(jié)構(gòu)很簡單，語法相當(dāng)于c的函數(shù)體，即由一對大括號括起來的語句序列，沒有過程或函數(shù)。聲明語句、表達式語句及控制語句的寫法都與c類似，但規(guī)定：一條聲明語句只能聲明一個整型變量，沒有數(shù)組；控制語句只是if、for和while三個語句，這三個語句本身也可以包含語句序列；表達式僅局限于布爾表達式和整型算術(shù)表達式，布爾表達式由對兩個算術(shù)表達式的比較組成，該比較使用<,>,<=,>=,==,!=比較運算符；算術(shù)表達式可以包括整型常數(shù)、變量以及+,－,*,/這四個運算符。另外，還可以有復(fù)合語句。用read和write語句實現(xiàn)輸入輸出。注釋用/*和*/括起來，但注釋不能嵌套。實驗原理及基本技術(shù)路線圖（方框原理圖或程序流程圖）實驗所用的產(chǎn)生式：<程序>→‘{’<聲明序列><語句序列>‘}’<聲明序列>→<聲明語句>{<聲明語句>}<聲明語句>→int<標(biāo)志符>;<語句序列>→<語句>{<語句>}<語句>→<if語句>|<while語句>|<for語句>|<read語句>|<write語句>|<復(fù)合語句>|<表達式語句><if語句>→if(<表達式>)<語句>[else<語句>]<while語句>→while(<表達式>)<語句><for語句>→for(<表達式>;<表達式>;<表達式>)<語句><read語句>→read<標(biāo)識符>;<write語句>→write<表達式>;<復(fù)合語句>→‘{’<語句序列>‘}’<表達式語句>→<表達式>;|;<表達式>→<布爾表達式>|<標(biāo)志符>=<布爾表達式><布爾表達式>→<算術(shù)表達式>|<算術(shù)表達式>(>|<|>=|<=|==|!=)<算術(shù)表達式><算術(shù)表達式>→<項>{(+|-)<項>}<項>→<因子>{(*|/)<因子>}<因子>→(<算術(shù)表達式>)|<標(biāo)識符>|<無符號整數(shù)>實驗中自定義的函數(shù)：intparse();語法分析主函數(shù)intprogram();<程序>intstatement();<語句>intexpression_stat();<表達式語句>intexpression();<表達式>intbool_expr();<布爾表達式>intadditive_expr();<算術(shù)表達式>intterm();<項>intfactor();<因子>intif_stat();<if語句>intwhile_stat();<while語句>intfor_stat();<for語句>intwrite_stat();<write語句>intread_stat();<read語句>intdeclaration_stat();<聲明語句>intdeclaration_list();<聲明序列>intstatement_list();<語句序列>intcompound_stat();<復(fù)合語句>所用儀器、材料（設(shè)備名稱、型號、規(guī)格等或使用軟件）開發(fā)環(huán)境/平臺：vc++6.0實驗器材：兼容計算機一臺實驗方法、步驟（或：程序代碼或操作過程）實驗源代碼：#include<stdio.h>#include<ctype.h>#include<conio.h>#include<string.h>intparse();intprogram();intstatement();intexpression_stat();intexpression();intbool_expr();intadditive_expr();intterm();intfactor();intif_stat();intwhile_stat();intfor_stat();intwrite_stat();intread_stat();intdeclaration_stat();intdeclaration_list();intstatement_list();intcompound_stat();chartoken[20],token1[40];//token保存單詞符號，token1保存單詞值charScanout[300];//保存詞法分析輸出文件名longcount=0;FILE*fp;//用于指向輸入輸出文件的指針voidmain(){strcpy(Scanout,"輸出.txt");parse();}//語法分析程序intparse(){ intes=0; if((fp=fopen(Scanout,"r"))==NULL) {printf("\n打開%s錯誤!\n",Scanout); es=10; } if(es==0)es=program(); printf("=====語法分析結(jié)果!======\n"); switch(es) { case0:printf("語法分析成功!\n");break; case10:printf("打開文件%s失敗!\n",Scanout);break; case1:printf("缺少{!\n");break; case2:printf("缺少}!\n");break; case3:printf("缺少標(biāo)識符!\n");break; case4:printf("少分號!\n");break; case5:printf("缺少(!\n");break; case6:printf("缺少)!\n");break; case7:printf("缺少操作數(shù)!\n");break; case8:printf("缺少運算符!\n");break; } fclose(fp); return(es);}voidget(){ fscanf(fp,"%s%s\n",&token,&token1); printf("%s%s\n",token,token1); count++;}voidback(intj)//文件指針回退一位{ inti; printf("文件指針回退%d位!\n",j); rewind(fp); for(i=0;i<count;i++) { fscanf(fp,"%s%s\n",&token,&token1); }}//<程序>::={<聲明序列><語句序列>}//program::='{'<declaration_list><statement_list>'}'intprogram(){intes=0; get();if(strcmp(token,"{"))//判斷是否'{'{ es=1; return(es);}es=declaration_list();if(es>0)return(es);es=statement_list();if(es>0)return(es);if(strcmp(token,"}"))//判斷是否'}'{ es=2; return(es);}return(es);}//<聲明序列>::=<聲明序列><聲明語句>|<聲明語句>//<declaration_list>::=//<declaration_list><declaration_stat>|<declaration_stat>//改成<declaration_list>::={<declaration_stat>}intdeclaration_list(){ intes=0; get(); while(strcmp(token,"int")==0) { es=declaration_stat(); if(es>0)return(es); } return(es);}//<聲明語句>::=int<變量>；//<declaration_stat>::=intID;intdeclaration_stat(){ intes=0; get(); if(strcmp(token,"ID")) return(es=3);//不是標(biāo)識符 get(); if(strcmp(token,";")) return(es=4); get(); return(es);}//<語句序列>::=<語句序列><語句>|<語句>//<statement_list>::=<statement_list><statement>|<statement>//改成<statement_list>::={<statement>}intstatement_list(){ intes=0; while(strcmp(token,"(")==0||strcmp(token,"NUM")==0||strcmp(token,"ID")==0||strcmp(token,"if")==0||strcmp(token,"while")==0||strcmp(token,"for")==0||strcmp(token,"read")==0||strcmp(token,"write")==0||strcmp(token,"{")==0) { es=statement(); if(es>0)return(es); get(); } returnes;}//<語句>::=<if語句>|<while語句>|<for語句>|<read語句>//|<write語句>|<復(fù)合語句>|<表達式語句>//<statement>::=<if_stat>|<while_stat>|<for_stat>//|<compound_stat>|<expression_stat>intstatement()//error；；；；；；{ intes=0; if(strcmp(token,"if")==0) { es=if_stat(); returnes; } if(strcmp(token,"while")==0) { es=while_stat(); returnes; } if(strcmp(token,"for")==0) { es=for_stat(); returnes; } if(strcmp(token,"read")==0) { es=read_stat(); returnes; } if(strcmp(token,"write")==0) { es=write_stat(); returnes; } if(strcmp(token,"{")==0) { es=compound_stat(); returnes; } else { es=expression_stat(); returnes; } returnes; }//<IF語句>::=if(<表達式>)<語句>[else<語句>]//<IF_stat>::=if(<expr>)<statement>[else<statement>]intif_stat(){ intes=0; inttemp=0; get(); if(strcmp(token,"(")==0) { get(); if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) { es=expression(); } else if(strcmp(token,"ID")) return(es=3); else if(strcmp(token,"NUM")) return(es=7); get(); if(strcmp(token,")")==0) { get(); es=statement(); temp=es; if(es>0)returnes; 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; returnes; } } else es=5; returnes;}//<while語句>::=while(<表達式>)<語句>//<while_stat>::=while(<expr>)<statement>intwhile_stat(){ intes=0; get(); if(strcmp(token,"(")==0) { get(); if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) { es=expression(); } else if(strcmp(token,"ID")) return(es=3); else if(strcmp(token,"NUM")) return(es=7); get(); if(strcmp(token,")")==0) { get(); es=statement(); returnes; } } else { es=5; returnes; } returnes;}//<for語句>::=for(<表達式>;<表達式>;<表達式>)<語句>//<for_stat>::=for(<expr>,<expr>,<expr>)<statement>intfor_stat(){ intes=0; get(); if(strcmp(token,"(")==0) { get(); if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) { es=expression(); if(es>0)returnes; } else if(strcmp(token,"ID")) return(es=3); else if(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)returnes; } else if(strcmp(token,"ID")) return(es=3); else if(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)returnes; } else if(strcmp(token,"ID")) return(es=3); else if(strcmp(token,"NUM")) return(es=7); get(); if(strcmp(token,")")==0) { get(); es=statement(); returnes; } else { es=6; returnes; } } else { es=4; returnes; } } else { es=4; returnes; } } else { es=5; returnes; } returnes; }//<write_語句>::=write<表達式>;//<write_stat>::=write<expression>;intwrite_stat(){ intes=0; get(); if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) { es=expression(); if(es>0)returnes; get(); if(strcmp(token,";"))return4; } else if(strcmp(token,"ID")) return(es=3); else if(strcmp(token,"NUM")) return(es=7); returnes;}//<read_語句>::=read<變量>;//<read_stat>::=readID;intread_stat(){ intes=0; get(); if(strcmp(token,"ID")) return(es=3);//不是標(biāo)識符 get(); if(strcmp(token,";"))return4; returnes;}//<復(fù)合語句>::={<語句序列>}//<compound_stat>::='{'<statement_list>'}'intcompound_stat(){//復(fù)合語句函數(shù) intes=0; get(); es=statement_list(); if(es>0)returnes; if(strcmp(token,"}"))return(es=2); returnes;}//<表達式語句>::=<表達式>;|;//<expression_stat>::=<expression>;|;intexpression_stat(){ intes=0; if(strcmp(token,";")==0)returnes; else { if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) { es=expression(); if(es>0)returnes; } get(); if(strcmp(token,";"))return4; } returnes;}//<表達式>::=<標(biāo)識符>=<布爾表達式>|<布爾表達式>//<expr>::=ID=<bool_expr>|<bool_expr>intexpression(){ intes=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)returnes; } else { count-=2; back(2); get(); if(strcmp(token,"ID")==0||strcmp(token,"NUM")==0||strcmp(token,"(")==0) es=bool_expr(); } } returnes;}//<布爾表達式>::=<算術(shù)表達式>|<算術(shù)表達式>(>|<|>=|<=|==|!=)<算術(shù)表達式>//<bool_expr>::=<additive_expr>//|<additive_expr>(>|<|>=|<=|==|!=)<additive_expr>intbool_expr(){ intes=0; es=additive_expr(); if(es>0)returnes; get(); if(strcmp(token,">")==0||strcmp(token,"<")==0||strcmp(token,">=")==0||strcmp(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)returnes; } else//keystep { count--; back(1); } returnes;}//<算術(shù)表達式>::=<項>{(+|-)<項>}//<additive_expr>::=<term>{(+|-)<term>}intadditive_expr(){ intes=0; es=term(); if(es>0)returnes; 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)returnes; } else//keystep { count--; back(1); } r