Class If

basex-core/src/main/java/org/basex/query/expr/If.java:24–275

If expression. @author BaseX Team, BSD License @author Christian Gruen

 * @author Christian Gruen
 */
public final class If extends Arr {
  /** Condition. */
  public Expr cond;

  /**
   * Constructor with empty 'else' branch.
   * @param info input info (can be {@code null})
   * @param cond condition
   * @param branch1 'then' branch
   */
  public If(final InputInfo info, final Expr cond, final Expr branch1) {
    this(info, cond, branch1, Empty.VALUE);
  }

  /**
   * Constructor.
   * @param info input info (can be {@code null})
   * @param cond condition
   * @param branch1 'then' branch
   * @param branch2 'else' branch
   */
  public If(final InputInfo info, final Expr cond, final Expr branch1, final Expr branch2) {
    super(info, Types.ITEM_ZM, branch1, branch2);
    this.cond = cond;
  }

  @Override
  public void checkUp() throws QueryException {
    checkNoUp(cond);
    checkAllUp(exprs);
  }

  @Override
  public Expr compile(final CompileContext cc) throws QueryException {
    cond = cond.compile(cc);

    final int el = exprs.length;
    for(int e = 0; e < el; e++) {
      exprs[e] = cc.compileOrError(exprs[e], false);
    }
    return optimize(cc);
  }

  @Override
  public Expr optimize(final CompileContext cc) throws QueryException {
    if(EMPTY.is(cond)) {
      // if(empty(A)) then B else C → if(exists(A)) then C else B
      cond = cc.function(EXISTS, cond.info(info), cond.arg(0));
      swap();
      cc.info(QueryText.OPTSWAP_X, this);
    } else if(NOT.is(cond)) {
      // if(not(A)) then B else C → if(A) then C else B
      cond = cond.arg(0);
      swap();
      cc.info(QueryText.OPTSWAP_X, this);
    }
    // if(exists($nodes)) → if($nodes)
    cond = cond.simplifyFor(Simplify.EBV, cc);