S語言詞法分析器設計

實驗1-4S語言詞法分析器設計PAGEPAGE4實驗1-3S語言詞法分析器設計一、實驗名稱：S語言詞法分析器設計二、實驗目的：通過手工編寫簡化C語言詞法分析器，熟悉并深入理解編譯程序詞法分析器的工作原理。三、實驗內(nèi)容：1．根據(jù)保留字和特殊符號表能區(qū)分出源文件中的保留字、普通標識符和特殊符號，并能進行簡單的錯誤處理。2．設計詞法分析器模塊調(diào)用結(jié)構(gòu)圖和各模塊流程圖。3．程序源代碼。4．程序的執(zhí)行結(jié)果：輸入文件，輸出結(jié)果文件及屏幕信息。四、實驗中出現(xiàn)的問題及解決方法。遇到問題及解決：1、關(guān)于注釋//和除號/。需要區(qū)分，在isanotation函數(shù)中。2、關(guān)于遇到空格時回退，一開始沒有懂，后來經(jīng)過同學講解，明白了如何回退的。3、關(guān)于詞法分析器的思想過程，經(jīng)過老師再三講解，已經(jīng)大致明白，具體步驟，在最后體會部分中。五、程序結(jié)構(gòu)和代碼程序結(jié)構(gòu)：代碼：#include<stdio.h>#include<stdlib.h>#include<string>#include<iostream>usingnamespacestd;//關(guān)鍵字表stringkeywords[20]={"include","void","main","int","char","float","double","if","else","then","break","continue","for","do","while","printf","scanf","begin","end","return"};charaa[99999]="";//關(guān)鍵字表初始為空stringid[10000];intpp=0;//常數(shù)表stringnu[10000];intqq=0;//初始化函數(shù)voidinitscanner(){inti=0;FILE*fp;if((fp=fopen("源程序.txt","r"))==NULL)//打開源程序文件{printf("沒有找到此文件!");exit(0);}charch=fgetc(fp);while(ch!=EOF){aa[i]=ch;i++;ch=fgetc(fp);}fclose(fp);}intdecide1(chara)//判斷是否是字母{if((a>='a'&&a<='z')||(a>='A'&&a<='Z'))return1;elsereturn0;}intdecide2(chara)//判斷是否是數(shù)字{if(a>='0'&&a<='9')return1;elsereturn0;}intisalpha(intst)//識別保留字和標識符{charwordbuf[20]="";intn=0;for(;;){wordbuf[n]=aa[st];st++;n++;if((decide2(aa[st])==1)||(decide1(aa[st])==1)||(aa[st]=='_'))wordbuf[n]=aa[st];elsebreak;}intflag=0;for(intk=0;k<20;k++){if(strcmp(keywords[k].c_str(),wordbuf)==0)flag=1;}if(flag==0){intflagg=-1;for(intt=0;t<pp;t++){if(strcmp(id[t].c_str(),wordbuf)==0){flagg=t;}}if(flagg!=-1)printf("(id,%d)",flagg);else{id[pp]=wordbuf;printf("(id,%d)",pp);pp++;}}else{printf("(");for(inti=0;i<n;i++){printf("%c",wordbuf[i]);}printf(",-)");}returnst;}intisnumber(intst)//識別數(shù)字{charnumbuf[20]="";intn=0;}elseif(aa[st]=='='){st++;printf("(/*,-)");}elseprintf("(/,-)");returnst;}intisother(intst)//函數(shù)識別其他特殊字符{switch(aa[st]){case'=':st++;if(aa[st]=='='){st++;printf("(rlop,==)");}elseprintf("(rlop,=)");break;case'+':st++;if(aa[st]=='='){st++;printf("(+=,-)");}elseif(aa[st]=='+'){st++;printf("(++,-)");}elseprintf("(+,-)");break;case'-':st++;if(aa[st]=='='){st++;printf("(-=,-)");}elseif(aa[st]=='-'){st++;printf("(--,-)");}elseprintf("(-,-)");break;case'*':st++;if(aa[st]=='='){st++;printf("(*=,-)");}else printf("(*,-)");break;case'>':st++;if(aa[st]=='='){st++;printf("(rlop,>=)");}elseprintf("(rlop,>)");break;case'<':st++;if(aa[st]=='='){st++;printf("(rlop,<=)");}elseprintf("(rlop,<)");break;case'%':st++;if(aa[st]=='='){st++;printf("(\%=,-)");}elseprintf("(\%,-)");break;case'!':st++;if(aa[st]=='='){st++;printf("(!=,-)");}else printf("(!,錯誤!)");break;case'&':st++;if(aa[st]=='&'){st++;printf("(&&,-)");}elseprintf("(&,錯誤)");break;case'|':st++;if(aa[st]=='|'){st++;printf("(||,-)");}elseprintf("(|,錯誤)");break;case'{':st++;printf("({,-)");break;case'}':st++;printf("(},-)");break;case'(':st++;printf("((,-)");break;case')':st++;printf("(),-)");break;case'[':st++;printf("([,-)");break;case']':st++;printf("(],-)");break;case':':st++;printf("(:,-)");break;case'#':st++;printf("(#,-)");break;case';':st++;printf("(;,-)");break;case'.':st++;printf("(.,-)");break;case',':st++;printf("(,,-)");break;case'':st++;break;case' ':st++;break;case10:st++;printf("\n");break;case34:st++;printf("(\",-)");break;case39:st++;printf("(',-)");break;default:printf("(%c,錯誤)",aa[st]);st++;}returnst;}intlexscan(intst)//根據(jù)讀入的單詞的第一個字符確定調(diào)用不同的單詞識別函數(shù){if(decide1(aa[st])==1)//如果是字母st=isalpha(st);elseif(decide2(aa[st])==1)//如果是數(shù)字st=isnumber(st);elseif(aa[st]=='/')//如果是標識符或關(guān)鍵字st=isanotation(st);elsest=isother(st);//其他特殊字符returnst;}voidscanner()//若文件未結(jié)束，反復調(diào)用lexscan函數(shù)識別單詞{inti=0;while(aa[i]!=NULL)i=lexscan(i);}voidprint(){cout<<endl;cout<<endl<<"關(guān)鍵字、標示符表如下："<<endl;cout<<"============================================="<<endl;for(inti=0;i<pp;i++)cout<<i<<""<<id[i]<<endl;cout<<"============================================="<<endl;cout<<endl;cout<<"常數(shù)表如下："<<endl;cout<<"============================================="<<endl;for(intj=0;j<qq;j++)cout<<j<<"