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语法分析
#include<stdio.h> #include<string.h> char prog[80],token[6]; char ch; int syn,p,m,n,sum,kk=0; char * rwtab[6]={"begin","if","then","while","do","end"}; main() { p=0; printf("\nplease intput string:"); do { ch=getchar(); prog[p++]=ch; }while(ch!=‘#‘); p=0; scaner(); lrparser(); getch(); } /*词法扫描程序:*/ scaner() { for(n=0;n<8;n++) token[n]=NULL; m=0; ch=prog[p++]; while(ch==‘ ‘)ch=prog[p++]; if((ch<=‘z‘&&ch>=‘a‘)||(ch<=‘Z‘&&ch>=‘A‘)) { while((ch<=‘z‘&&ch>=‘a‘)||(ch<=‘Z‘&&ch>=‘A‘)||(ch<=‘9‘&&ch>=‘0‘)) { token[m++]=ch; ch=prog[p++]; } token[m++]=‘\0‘; ch=prog[--p]; syn=10; for(n=0;n<6;n++) if(strcmp(token,rwtab[n])==0) { syn=n+1; break; } } else if((ch<=‘9‘&&ch>=‘0‘)) { sum=0; while((ch<=‘9‘&&ch>=‘0‘)) { sum=sum*10+ch-‘0‘; ch=prog[p++]; } ch=prog[--p]; syn=11; } else switch(ch) { case ‘<‘:m=0;token[m++]=ch; ch=prog[p++]; if(ch==‘>‘) { syn=21; token[m++]=ch; } else if(ch==‘=‘) { syn=22; token[m++]=ch; } else { syn=20; ch=prog[--p]; } break; case ‘>‘:token[m++]=ch; ch=prog[p++]; if(ch==‘=‘) { syn=24; token[m++]=ch; } else { syn=23; ch=prog[--p]; } break; case ‘:‘:token[m++]=ch; ch=prog[p++]; if(ch==‘=‘) { syn=18; token[m++]=ch; } else { syn=17; ch=prog[--p]; } break; case ‘+‘:syn=13;token[0]=ch;break; case ‘-‘:syn=14;token[0]=ch;break; case ‘*‘:syn=15;token[0]=ch;break; case ‘/‘:syn=16;token[0]=ch;break; case ‘:=‘:syn=18;token[0]=ch;break; case ‘<>‘:syn=21;token[0]=ch;break; case ‘<=‘:syn=22;token[0]=ch;break; case ‘>=‘:syn=24;token[0]=ch;break; case ‘=‘:syn=25;token[0]=ch;break; case ‘;‘:syn=26;token[0]=ch;break; case ‘(‘:syn=27;token[0]=ch;break; case ‘)‘:syn=28;token[0]=ch;break; case ‘#‘:syn=0;token[0]=ch;break; default:syn=-1; } } lrparser() { if(syn==1) { scaner(); yucu(); if(syn==6) { scaner(); if((syn==0)&&(kk==0)) printf("sucess"); } else { if(kk!=1) printf("lost end error!"); kk=1; } } else { printf("output of begin is error!"); kk=1; } return; } yucu() { statement(); while(syn==26) { scaner(); statement(); } return; } statement() { if(syn==10) { scaner(); if(syn==18) { scaner(); expression(); } else { printf("output of equal is error!"); kk=1; } } else { printf("input of sentence is error!"); kk=1; } return; } expression() { term(); while(syn==13||syn==14) { scaner(); term(); } return; } term() { factor(); while(syn==15||syn==16) { scaner(); factor(); } return; } factor() { if(syn==10||syn==11)scaner(); else if(syn==27) { scaner(); expression(); if(syn==28)scaner(); else { printf("output ‘)‘ is error!"); kk=1; } } else { printf("output expression is error!"); kk=1; } return; }
语法分析
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