interpreter1.rkt

; Vanessa Melikian, Vishal Shah, Catherine Tsuei

(require "simpleParser.scm")
; Unary operator??

; takes an arithmetic expression and returns the value
(define MValueInt
  (lambda (expression)
    (cond
      ((number? expression) expression)
      ((eq? '+ (operator expression)) (+ (MValueInt (operand1 expression)) (MValueInt (operand2 expression))))
      ((eq? '- (operator expression)) (- (MValueInt (operand1 expression)) (MValueInt (operand2 expression))))
      ((eq? '* (operator expression)) (* (MValueInt (operand1 expression)) (MValueInt (operand2 expression))))
      ((eq? '/ (operator expression)) (quotient (MValueInt (operand1 expression)) (MValueInt (operand2 expression))))
      ((eq? '% (operator expression)) (remainder (MValueInt (operand1 expression)) (MValueInt (operand2 expression))))
      (else (error 'badop "Undefined operator")))))

; takes a prefix expression and returns the operator
(define operator
  (lambda (e)
    (car e)))

; returns the first operand of an expression
(define operand1 cadr)

; returns the second operand of an expression
(define operand2 caddr)

; TODO: make sure that variables can work here
; takes a comparative expression and returns the boolean result
(define MBoolComparison?
  (lambda (comparison)
    (cond
      ((number? comparison) comparison)
      ((eq? '== (operator comparison)) (eq? (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison))))
      ((eq? '!= (operator comparison)) (not (eq? (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison)))))
      ((eq? '< (operator comparison)) (< (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison))))
      ((eq? '> (operator comparison)) (> (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison))))
      ((eq? '<= (operator comparison)) (<= (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison))))
      ((eq? '>= (operator comparison)) (>= (MValueComparison? (operand1 comparison)) (MValueComparison? (operand2 comparison))))
      (else (error 'badop "Undefined operator")))))

; TODO: no numbers allowed, make sure expressions have true/false values
; takes a logical expression and returns the boolean result
(define MBoolLogicOperators?
  (lambda (logicExpressio
    (cond
      ((eq? '#t logicExpression) #t)
      ((eq? '#f logicExpression) #f)
      ((eq? '&& (operator logicExpression)) (and (MBoolLogicOperators? (operand1 logicExpression)) (MBoolLogicOperators? (operand2 logicExpression))))
      ((eq? '|| (operator logicExpression)) (or (MBoolLogicOperators? (operand1 logicExpression)) (MBoolLogicOperators? (operand2 logicExpression))))
      ((eq? '! (operator logicExpression)) (not (MBoolLogicOperators? (operand1 logicExpression))))
      (else (error 'badop "Undefined operator")))))

; takes a conditional expression & current state and returns the new state after evaluation
(define MStateIf
  (lambda (condition then else state)
    (if (MBool condition state) (MStateStatement(then state)) (MStateStatement(else state)))))

; takes a statement list & current state and returns the new state after evaluation
(define MStateStatementList
  (lambda (statementlist state)
    (if (null? statementlist)
        state
        (MStateStatementList (cdr statementlist) (MState (car statementlist) state)))))




(define MState
  (lambda (expression state)
    (cond
      ((eq? '= (operator expression)) ((MAssign (var expression) (value expression) state)))
      



; binding pairs --> "state"
; variable declaration (var variable) or (var variable value)

; returns the variable of an expression
(define var cadr)

; returns the value of an expression
(define value caddr)
  
; assignment (= variable expression)
  (define MAssign
    (lambda (expression state)
      (cond
        (Mstate (var expression)
       (eq? '= (operator expression)) ; may not need it based on the = check in MState
          (MBinding (var expression) (value expression) state)
      (else (error 'badop "Undefined operator"))))
  
; return (return expression)
  (define return
    (lambda (var state)
      (cond
        ((null? MValue(var state))
          (error 'undef "undeclared variable")
          (MValue(var state)))))
; if (if conditional then-statement optional-else-statement)
; while (while conditional body-statement)
   

  (define MStatement
  (lambda (statement state)
    (if (null? statement)
        state
        (MState(statement state)))))

  (define MStatement
    (lambda (var '=' val state)
     ( if (null? statement)
          state
          ((remove (Mvalue(var) state) (add (Mvalue(var) Mvalue(val) state)))))))

  (define add
    (lambda (name state)