/*
 * A header file for a simple lexer.  A lexer is just a device
 * used to subdivide a string into logical symbols.
 */

#ifndef LEXER_H
#define LEXER_H

typedef enum {LPAREN, RPAREN, OPERATOR, NUMBER, EOS, ERROR} Lexeme;

typedef struct LexicalElement {
  Lexeme type;
  union {
    double num;   //numeric value
    char c;       //character value
  } value;
} LexicalElement;

/*
 * Return the next lexical element in the string s.
 *  Passing NULL into s, will cause the lexer to read the next element out
 *  of the last string passed in.
 */
LexicalElement nextElement(char *s);


#endif