bak0016.rkt

#lang plai

;;Bryant Kelley bak0016

(require racket/path)

;;creates global list variable called tokens
;;reads in every line from tokens file and saves
;;each token/lexeme pair as a separate list item
;(define tokens (file->lines (string->path "D:\\Dropbox\\auburn_faculty\\RacketPrograms\\tokens")));;school computer
(define tokens (file->lines (string->path "/Users/bryant/Documents/COMP 3220/Assignment 3/tokens.txt")));;home computer

(define error_count 0)

;;helper function
;;retrieves the first token from the list of tokens
(define current_token
  (lambda ()
    (regexp-split #px" " (car tokens))
    );end lambda
  );end current_token

;;helper function
;;removes one token from the tokens list
;;so that current_token function always extracts
;;the next available token
(define next_token
  (lambda ()
    (set! tokens (cdr tokens))
    (cond
      ((null? tokens)
       (display "No more tokens to parse!")
       (newline)
       (display "Exiting prematurely, no eof found")
       (newline)
       (display "Errors found: ")
       (display error_count)
       (newline)
       (exit));end null tokens
      (else
       (cond
         ((equal? (car (current_token)) "whitespace")
          (next_token);call yourself again
          )     
         );end cond
       );end else
      );end cond
    );end lambda
  );end next_token
    
;;checks ID rule
;;if current_token is an id token
;;displays message found + lexeme that was encountered
;;in addition, also displays when entering or leaving
;;function (parse trace)
;;if current_token is not id, displays an error message
(define id
  (lambda ()
    (display "Entering <id>")
    (newline)
    (cond
      ((equal? (car (current_token)) "id")
       (display "Found ")
       (display (second (current_token)))
       (newline)
       (next_token)
       (display "Leaving <id>")
       (newline)
       );end first equality check in condition
      (else
       (display "Not an id token: Error")
       (newline)
       (+ error_count 1)
       );end else statement
      );end condition block
    );end lambda
  );end id

;;checks int rule
;;if current_token is an int token
;;displays message found + lexeme that was encountered
;;in addition, also displays when entering or leaving
;;function (parse trace)
;;if current_token is not int, displays an error message
(define int
  (lambda ()
    (display "Entering <int>")
    (newline)
    (cond
      ((equal? (car (current_token)) "int")
       (display "Found ")
       (display (second (current_token)))
       (newline)
       (next_token)
       (display "Leaving <int>")
       (newline)
       );end first equality check in condition
      (else
       (display "Not an int token: Error")
       (newline)
       (+ error_count 1)
       );end else statement
      );end condition block
    );end lambda
  );end int

;;checks factor rule
;;prints terminals along the way, calling the appropriate function
;;for non-terminals
;;displays message found + lexeme that was encountered
;;in addition, also displays when entering or leaving
;;function (parse trace)
;;if current_token is not (
(define factor
  (lambda ()
    (display "Entering <factor>")
    (newline)
    (cond
      ((equal? (car (current_token)) "(")
       (display "Found ")
       (display (second (current_token)));should display a (
       (newline)
       (next_token)
       (exp)
       (cond
         ((equal? (car (current_token)) ")")
          (display "Found ")
          (display (second (current_token)));should display a )
          (newline)
          (next_token)
          (display "Leaving <factor>")
          (newline)
          );end
         (else
          (display "Not a ( token: Error")
          (newline)
          (+ error_count 1)
          );end else
         );end cond
       );end first equality check in condition
      ((equal? (car (current_token)) "id")
       (id)
       (display "Leaving <factor>")
       (newline)
       );end second equality check in condition
      ((equal? (car (current_token)) "int")
       (int)
       (display "Leaving <factor>")
       (newline)
       );end third equality check in condition
      (else
       (display "Not an factor token: Error")
       (newline)
       (+ error_count 1)
       );end else statement
      );end condition block
    );end lambda
  );end define factor

;;checks exp rule
;;prints terminals along the way, calling the appropriate function
;;for non-terminals
;;displays message found + lexeme that was encountered
;;in addition, also displays when entering or leaving
;;function (parse trace)
(define exp
  (lambda ()
    (display "Entering <exp>")
    (newline)
    (term)
    (etail)
    (display "Leaving <exp>")
    (newline)
    );end lambda
  );end define exp

(define assign
  (lambda ()
    (display "Entering <assign>")
    (newline)
    (id)
    (cond
      ((equal? (car (current_token)) "=")
       (display "Found ")
       (display (second (current_token)));should display a =
       (newline)
       (next_token)
       (exp)
       (display "Leaving <assign>")
       (newline)
       );end first equality check
      (else
       (display "Not a = token: Error")
       (newline)
       (+ error_count 1)
       );end else statement
      );end condition block
    );end lambda
  );end define assign

(define term
  (lambda ()
    (display "Entering <term>")
    (newline)
    (factor)
    (ttail)
    (display "Leaving <term>")
    (newline)
    );end lambda
  );end define term

(define etail
  (lambda ()
    (display "Entering <etail>")
    (newline)
    (cond
      ((equal? (car (current_token)) "+")
       (display "Found ")
       (display (second (current_token)));should display a +
       (newline)
       (next_token)
       (factor)
       (etail)
       (display "Leaving <etail>")
       (newline)
       );end first cond check
      ((equal? (car (current_token)) "-")
       (display "Found ")
       (display (second (current_token)));should display a -
       (newline)
       (next_token)
       (factor)
       (etail)
       (display "Leaving <etail>")
       (newline)
       );end second cond check
      (else
       (display "Not an etail token.")
       (newline)
       (display "Leaving <etail>")
       (newline)
       );end else
      );end cond
    );end lambda
  );end define etail

(define ttail
  (lambda ()
    (display "Entering <ttail>")
    (newline)
    (cond
      ((equal? (car (current_token)) "*")
       (display "Found ")
       (display (second (current_token)));should display a *
       (newline)
       (next_token)
       (factor)
       (ttail)
       (display "Leaving <ttail>")
       (newline)
       );end first cond check
      ((equal? (car (current_token)) "/")
       (display "Found ")
       (display (second (current_token)));should display a /
       (newline)
       (next_token)
       (factor)
       (ttail)
       (display "Leaving <ttail>")
       (newline)
       );end second cond check
      
      (else
       (display "Not a ttail token.")
       (newline)
       (display "Leaving <ttail>")
       (newline)
       );end else
      );end cond
    );end lambda
  );end define etail

(define stmt
  (lambda ()
    (display "Entering <stmt>")
    (newline)
    (cond
      ((equal? (car (current_token)) "print")
       (display "Found ")
       (display (second (current_token)));should display print
       (newline)
       (next_token)
       (exp)
       (display "Leaving <stmt>")
       (newline)
       (stmt)
       )
      ((equal? (car (current_token)) "id")
       (assign)
       (display "Leaving <stmt>")
       (newline)
       (stmt)
       )
      ((equal? (car (current_token)) "eof")
       (display  "Found ")
       (display (second (current_token)))
       (display "Leaving <stmt>")
       (newline)
       )
      (else
       (display "Not a <stmt>: Error")
       (newline)
       (+ error_count 1)
       );end else
    );end cond
   );end lambda
  );end define stmt

(define pgm
  (lambda ()
    (display "Entering <pgm>")
    (newline)
    (stmt)
    (cond
      ((equal? (car (current_token)) "eof")
       (display "End of File")
       (newline)
       )
      )
    (display "Leaving <pgm>")
    (newline)
    (display "Errors found: ")
    (display error_count)
    (newline)
    )
  )

;;test function to test whether or not next_token
;;will actually terminate program when it encounters
;;eof
(define tt
  (lambda ()
    (display (current_token))
    (newline)
    (next_token)
    (tt)
    )
  )