编译原理语法分析(3)

yufa0.SYM = yufa2[mm].SYM; exp(); } else { exp(); if ((yufa0.SYM == \\ { mm++; yufa0.SYM = yufa2[mm].SYM; exp(); } else

}

error15();//条件语句出错，缺少界符

//odd是否存在？ }

void exp()// → [+|-]{} { while((yufa0.SYM == \ { mm++; yufa0.SYM = yufa2[mm].SYM; term();// } term(); while ((yufa0.SYM == \→ +|- { mm++; yufa0.SYM = yufa2[mm].SYM; term(); } }

void term()// → {} { factor(); while ((yufa0.SYM == \→ *|/ { mm++; yufa0.SYM = yufa2[mm].SYM;

}

}

factor();//factor()

void factor()//→||() { if (yufa0.SYM == \ { mm++; yufa0.SYM = yufa2[mm].SYM; } else if (yufa0.SYM == \ { mm++; yufa0.SYM = yufa2[mm].SYM; } else if (yufa0.SYM == \ { mm++; yufa0.SYM = yufa2[mm].SYM; exp(); if (yufa0.SYM == \ { mm++; yufa0.SYM = yufa2[mm].SYM; } else error7(); //缺少右括号 } else error8();//缺少左括号 }

string Concat(char ch,string strToken) { strToken += ch; return strToken; }

int IsLetter(char c ) //判断字母 { if (((c <= 'z')&&(c >= 'a')) || ((c <= 'Z')&&(c >= 'A'))) return 1; else return 0; }

int IsDigit(char c) //判断数字 {

}

if ((c >= '0')&&(c <= '9')) return 1; else return 0;

int IsKey(string StrToken) //判断保留字 { int i; for (i = 0; i<15; i++) { if (key[i].compare(StrToken) == 0) return 1; } return 0; }

void getsym(fstream &file) { string StrToken = \

// if (ch == ' ' || ch == '\\t' || ch == '\\n') //滤掉空白字符 // ch = file.get(); if (IsLetter(ch)) { while (IsLetter(ch) || IsDigit(ch)) { StrToken = Concat(ch,StrToken); ch = file.get(); } if (IsKey(StrToken)) { int i; for (i = 0; i<15; i++) { if (key[i].compare(StrToken) == 0) yufa1.SYM = key[i]; } yufa1.strToken = StrToken; } else { yufa1.SYM = \ yufa1.strToken = StrToken;

} }

if (IsDigit(ch)) { StrToken = \ while(IsDigit(ch)) { StrToken = Concat(ch,StrToken); ch = file.get(); }

if(IsLetter(ch)) //数字后面跟字母，错误词法 { while(IsLetter(ch)||IsDigit(ch)) { StrToken = Concat(ch,StrToken); ch = file.get(); } cout <<\词法错误！(数字后面跟字母) \ } else yufa1.SYM = \ yufa1.strToken = StrToken; }

else switch (ch) {

case'+':{yufa1.SYM = \case'-':{yufa1.SYM = \case'*':{yufa1.SYM = \case'/':{yufa1.SYM = \case'(':{yufa1.SYM = \case')':{yufa1.SYM = \case'=':{yufa1.SYM = \case';':{yufa1.SYM = \case',':{yufa1.SYM = \case':': { ch = file.get(); if (ch == '=') { yufa1.SYM = \ yufa1.strToken = \ }

else

cout <<\词法错误（：后面没有=）\ ch = file.get(); break; }

case'>': { ch = file.get(); if (ch == '=') { yufa1.SYM = \ yufa1.strToken = \ } else { yufa1.SYM = \ yufa1.strToken = \ } ch = file.get(); break; }

case'<': { ch = file.get(); if (ch == '=') { yufa1.SYM = \ yufa1.strToken = \ } else if (ch == '>') { yufa1.SYM = \ yufa1.strToken = \ } else { yufa1.SYM = \ yufa1.strToken = \ } ch = file.get(); break;