The code implementing lexical analyzer covert C code to Java
sairam96
CODE.docx# include <stdio.h> <ctype.h>
/ *Global declarations */
/*Variables */
int charClass ;
char lexeme [100];
char nextChar
int lexLen;
int token;
int nextToken;
FILE *in_fp, *fopen
Void Add char();
Void Get char();
Void getnonblank();
Int lex();
/* character classes */
#define LETTER 0
#define DIGIT 1
#define UNKOWN 99
/* Token codes */
#define INT_LIT 10
#define IDENT 11
#define ASSIGN_OP 20
#define ADD_OP 21
#define SUB_OP 22
#define MULT_OP 23
#define DIV_OP 24
#define LEFT_PAREN 25
#define RIGHT_PAREN 26
/******************************************************/
/* main driver */
main() {
/* Open the input data file and process its contents */
if ((in_fp = fopen("front.in", "r")) == NULL)
printf("ERROR - cannot open front.in \n");
else
{
getChar();
do
{
lex();
} while (nextToken! = EOF);
}
}
/*****************************************************/
/* lookup - a function to lookup operators and parentheses and return the token */
int lookup(char ch) {
switch (ch) {
case '(': addChar();
nextToken = LEFT_PAREN;
break;
case ')':
addChar();
nextToken = RIGHT_PAREN;
break;
case '+':
addChar();
nextToken = ADD_OP;
break;
case '-': addChar();
nextToken = SUB_OP;
break;
case '*': addChar();
nextToken = MULT_OP;
break;
case '/': addChar();
nextToken = DIV_OP;
break;
default:
addChar();
nextToken = EOF;
break;
}
Return nextToken;
}
/*****************************************************/
/* addChar - a function to add nextChar to lexeme */
void addChar() {
if (lexLen <= 98) {
lexeme[lexLen++] = nextChar;
lexeme[lexLen] = 0;
}
Else
printf("Error - lexeme is too long \n");
}
/*****************************************************/
/* getChar - a function to get the next character of input and determine its character class */
void getChar() {
if ((nextChar = getc(in_fp)) = EOF) {
if (isalpha(nextChar)) charClass = LETTER;
else if (isdigit(nextChar)) charClass = DIGIT;
else charClass = UNKNOWN;
}
else charClass = EOF;
/*****************************************************/
/* getNonBlank - a function to call getChar until it returns a non-whitespace character */
void getNonBlank() {
while (isspace(nextChar)) getChar();
}
/
/*****************************************************/
/* lex - a simple lexical analyzer for arithmetic expressions */
int lex() {
lexLen = 0;
getNonBlank();
switch (charClass) {
/* Parse identifiers */
case LETTER:
addChar();
getChar();
while (charClass == LETTER || charClass == DIGIT) {
addChar();
getChar();
}
nextToken = IDENT; break;
/* Parse integer literals */
case DIGIT: addChar();
getChar();
while (charClass == DIGIT) {
addChar();
getChar();
}
nextToken = INT_LIT;
break;
/* Parentheses and operators */
case UNKNOWN: lookup(nextChar);
getChar();
break;
/* EOF */ case EOF:
nextToken = EOF;
lexeme[0] = 'E';
lexeme[1] = 'O';
lexeme[2] = 'F';
lexeme[3] = 0;
break; } /* End of switch */
printf("Next token is: %d, Next lexeme is %s\n",
nextToken, lexeme);
return nextToken; }
/* End of function lex */
