Compiler principle-Lexical analyzer

Sample input: If num > then num2 = + Else num2 = 0; #

Sample output:

#include "Cstdio" #include "CString" #include "cctype" Const int ERROR =-1; const int over = 0; const int BEGIN = 1;const in T END = 2;const int IF = 3;const int then = 4;const int when = 5;const int do = 6;const int const = 7;const int VAR = 8;c onst int call = 9; const int PROCEDURE = 10;const int ID = 11;const int number = 12;const int PLUS = 13;const int SUB = 14; const int STAR = 15;const int DIV = 16;const int MOD = 17;const int EQUAL = 18;//=const int NE =19;//<>const int LES S = 20;//<const int more = 21;//>const int LE = 22;//<=const int ME = 23;//>=const int ASSIGN = 24;//:=const I NT LPAR = 25;//(const int RPAR = 26;//) const int COMMA = 27;//,const int DOT = 28;//.const int semicolon = 29;//;char Buff  er[200]= {'};char ' str[20];//holds the string that makes up the word symbol */char ch;int n;int number;    Holds a constant (integer) int pstr,pbuffer; keyword int keywordnum=10; Keyword char keywords [10][10] = {"Begin", "End", "if", "then", "while", "does", "Const", "var", "Call", "procedure"};//constant table int Numofnumbers=0;int numtab[100];//variable table int Numofvars=0;char vartab[100][10];//read non-null character void Getbc () {ch=buffer[pbuffer++]; while (ch== ') ch=buffer[pbuffer++];} Fallback one character void retract () {ch=buffer[pbuffer--];}    Scan the contents of the buffer int scan () {//Initialize string pstr=0;    for (int i=0; i<20; ++i) {str[i]= ';    }//Initialize numeric constant number=0;    GETBC ();            if (Isalpha (CH)) {//Read identifier while (Isalpha (ch) | | isdigit (CH)) {str[pstr++]=ch;        ch = buffer[pbuffer++];        } str[pstr++]= ' + ';        int syn=11; Retract ();//fallback//Determine if the keyword for (int i=0; i<keywordnum; ++i) {if (strcmp (str,keywords[i)) =                =0)//string comparison {syn=i+1;            Break    }} return syn;            } else if (IsDigit (CH)) {while (IsDigit (CH)) {Number = number*10 + ch-' 0 ';        ch = buffer[pbuffer++];    } retract ();//fallback return number;   } else {     Switch (CH) {case ' + '://syn=13;            Str[0]=ch;        return PLUS;            Case '-'://syn=14;            Str[0]=ch;        return SUB;            Case ' * '://syn=15;            Str[0]=ch;        return STAR;            Case '/'://syn=16;            Str[0]=ch;        return DIV;            Case '% ': str[0]=ch;        return MOD;            Case ' = ': str[0]=ch;        return EQUAL;            Case ' < ': pstr=0;            Str[pstr++]=ch;            Ch=buffer[pbuffer++];                if (ch== ' > ') {str[pstr++]=ch;            return NE;                } else if (ch== ' = ') {str[pstr++]=ch;            return LE;                } else {retract ();            return less;        } break;            Case ' > ': pstr=0;            Str[pstr++]=ch; Ch=buffer[pbuFfer++];                if (ch== ' = ') {str[pstr++]=ch;            return ME;                } else {retract ();            return more;        } break;            Case ': ': pstr=0;            Str[pstr++]=ch;            Ch=buffer[pbuffer++];                if (ch== ' = ') {str[pstr++]=ch;            return ASSIGN;                } else {retract ();            return ERROR;        } break;            Case ' (': str[0]=ch;        return LPAR;            Case ') ': str[0]=ch;        return rpar;            Case ', ': str[0]=ch;        return COMMA;            Case '. ': str[0]=ch;        return DOT;            Case '; ': str[0]=ch;        return semicolon;            Case ' # ': str[0]=ch;        return over;        Default:return ERROR; }}}//Insert variable, return the position of the variable table int Insert_var (const char * str) {for (int i=0; i<numofvars; i++) {if (strcmp (Str,vartab[i]) ==0)//string comparison        {return i+1;    }} strcpy (VARTAB[NUMOFVARS++],STR); return numofvars;} Inserts an integer constant that returns the position int insert_num (int number) {for (int i=0; i<numofnumbers; i++) {if (numtab[i]==number)//character        Comparison of strings {return i+1;    }} Numtab[numofnumbers++]=number; return numofnumbers;} Main () {freopen ("In.txt", "R", stdin);//reads data from a file into printf ("\n\nthe explanation: \ n" "1. 1 to 10:keyword\n "" 2. 11:other indicators by user\n "" 3. 12:numbers\n "" 4.    29:operators\n ");    printf ("\nplease input string:\n");    input to buffer pbuffer=0;        do {Ch=getchar ();    Buffer[pbuffer++]=ch;    } while (ch!= ' # ');    Lexical analysis pbuffer=0;    int Loc,syn;        do {syn = scan ();            Switch (SYN) {case-1: printf ("error\n");Break            Case 12://Constant LOC = Insert_num (number);            printf ("(%2d,%2d)%d\n", syn,loc,number);        Break            Case 11://user Variable loc = insert_var (str);            printf ("(%2d,%2d)%s\n", syn,loc,str);        Break        Default://Keywords printf ("(%2d,-)%s\n", syn,str);    }} while (syn!=0); return 0;}

　　

Compiler principle-Lexical analyzer