Method: Sequel::SQL::BooleanExpression.invert

Defined in:
lib/sequel/sql.rb

.invert(ce) ⇒ Object

Invert the expression, if possible. If the expression cannot be inverted, raise an error. An inverted expression should match everything that the uninverted expression did not match, and vice-versa, except for possible issues with SQL NULL (i.e. 1 == NULL is NULL and 1 != NULL is also NULL).



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# File 'lib/sequel/sql.rb', line 463

def self.invert(ce)
  case ce
  when BooleanExpression
    case op = ce.op
    when :AND, :OR
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.collect{|a| BooleanExpression.invert(a)})
    else
      BooleanExpression.new(OPERTATOR_INVERSIONS[op], *ce.args.dup)
    end
  when ComplexExpression
    raise(Sequel::Error, "operator #{ce.op} cannot be inverted")
  else
    BooleanExpression.new(:NOT, ce)
  end
end