Description

#include 
#include 
#include 
#include 

/*
Something like Python

>> y = 2
>> z = 2
>> x = 3*y + 4/(2*z)

*/


/*
the only type: integer
everything is an expression
  statement   := END | expr END
  expr        := term expr_tail
  expr_tail   := ADDSUB term expr_tail | NIL
  term        := factor term_tail
  term_tail := MULDIV factor term_tail | NIL
  factor      := INT | ADDSUB INT | ADDSUB ID | ID ASSIGN expr | ID | LPAREN expr RPAREN
*/

#ifndef __LEX__
#define __LEX__
#define MAXLEN 256
typedef enum {UNKNOWN, END, INT, ID, ADDSUB, MULDIV, ASSIGN,
LPAREN, RPAREN} TokenSet;
char lexeme[MAXLEN];

extern int match (TokenSet token);
extern void advance(void);
#endif // __LEX__

static TokenSet getToken(void);
static TokenSet lookahead = UNKNOWN;

TokenSet getToken(void)
{
    int i;
    char c;

    while ( (c = fgetc(stdin)) == ' ' || c== '\t' );  // deal with space

    if (isdigit(c)) {
        lexeme[0] = c;
        c = fgetc(stdin);
        i = 1;
        while (isdigit(c) && i
  
Input
  
  
Output
  
  
Sample Input  Download
  

    
  
  
Sample Output  Download
  

    
  
  
  
  
  
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