gapt.expr.formula.fol.FOLExpression.scala Maven / Gradle / Ivy

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General Architecture for Proof Theory

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package gapt.expr.formula.fol

import gapt.expr.Expr
import gapt.expr.formula.fol.FOLPosition.getPositions

trait FOLExpression extends Expr {

  /**
   * Retrieves this expression's subexpression at a given position.
   *
   * @param pos The position to be retrieved.
   * @return The subexpression at pos.
   */
  def apply(pos: FOLPosition): FOLExpression = get(pos) match {
    case Some(f) => f
    case None    => throw new Exception("Position " + pos + " does not exist in expression " + this + ".")
  }

  /**
   * Retrieves this expression's subexpression at a given position, if there is one.
   *
   * @param pos The position to be retrieved.
   * @return If there is a subexpression at that position, return Some(that expression). Otherwise None.
   */
  def get(pos: FOLPosition): Option[FOLExpression] =
    FOLPosition.toHOLPositionOption(this)(pos).flatMap(get).asInstanceOf[Option[FOLExpression]]

  def replace(pos: FOLPosition, replacement: FOLExpression): FOLExpression =
    FOLPosition.replace(this, pos, replacement)

  /**
   * Tests whether this expression has a subexpression at a given position.
   *
   * @param pos The position to be tested.
   * @return Whether this(pos) is defined.
   */
  def isDefinedAt(pos: FOLPosition): Boolean = get(pos).isDefined

  /**
   * Finds all HOL positions of a subexpression in this expression.
   *
   * @param exp The subexpression to be found.
   * @return A list containing all positions where exp occurs.
   */
  def find(exp: FOLExpression): List[FOLPosition] = getPositions(this, _ == exp)

}