#include <stdio.h>
#include <ctype.h>

#include "lex.h"
#include "calc.h"



number val;


int lookahead()  /* returns next character without actually reading it */
{
  if( feof(stdin)) return EOF;
  int c = getchar();
  ungetc(c, stdin);
  return c;
}



void whitespaces() /* skips blanks */
{
  while( isblank(lookahead()) ) getchar();
  return;
  
}


int lex()
{
  int c;
  int cp;
  whitespaces();
  c = lookahead();
  if( c == EOF) return c;
  
  if( isdigit(c) || c == '.'){
    scanf(NUMFMT,&val);
    return NUMBER;
  }

  getchar(); /* advance anyway */

  if( c == '+' || c == '-'){
    /*
    ** could be a unary + or - in which case a digit should follow 
    */
    if( (cp = lookahead()) == '.' || isdigit(cp) ){
      scanf(NUMFMT,&val);
      if( c == '-') val = - val;
      return NUMBER;
    }
    return c;
  }

  switch(c){
  case '\n': 
  case '/' :
  case '*' : return c;
  case 'p' : return POP;
  case 'P' : return POPALL;
  default  : 
    return UNKNOWN;
  } /* switch */
}