/** COMP 411 Homework #0.5
  * Symbolic Boolean Expressions
  */

/** Symbolic boolean expression representation */
sealed abstract class BoolExp

// Literal Case Classes  ...
 

// Unary Operator Case Class ...

// Binary Operator Case Classes ...
  
// Ternary Operator Case Class

object BoolExp {
  
  /** Internal representation for if expressions */
  sealed abstract class IfExp
  
  // Three Case classes  ...

  // Convenience declarations for boolean constants
  // ! Scala convention is to capitalize the first letter for a constant
  // ! Such (capitalized) identifiers are treated as constants in match patterns
  val True = IVal(true)
  val False = IVal(false)
  
  /** Convert boolean expressions to internal
    * if-representation for further processing
    */
  def convertToIf(exp : BoolExp) : IfExp = ...

  /** Normalize the if-representation by making all condition-slots be literals */
  def normalize(exp : IfExp) : IfExp = ...
  
  /** Perform head normalization (Helper for normalize) */
  def headNormalize(test : IfExp, conseq : IfExp, alt : IfExp) : IfExp = ...

  /** Perform symbolic evaluation (simplification) on the given expression. */
  def eval(exp : IfExp, env : Map[String,Boolean]) : IfExp = ...

  /** Convert if-representation back to normal
   *  Maps several if-forms onto more concise boolean expressions
   */
  def convertToBool(exp : IfExp) : BoolExp = null
}