text: """
  Copyright 2013 Steven Diamond
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  """
  
  from noncvx_variable import NonCvxVariable
  import cvxpy.lin_ops.lin_utils as lu
  import numpy as np
  
  class Boolean(NonCvxVariable):
      """ A boolean variable. """
      # Sets the initial z value to a matrix of 0.5's.
      def init_z(self):
          self.z.value = np.zeros(self.size) + 0.5
  
      # All values set rounded to zero or 1.
      def _round(self, matrix):
          return np.around(matrix)
  
      # Constrain all entries to be the value in the matrix.
      def _fix(self, matrix):
          return [self == matrix]
  
      # In the relaxation, we have 0 <= var <= 1.
      def canonicalize(self):
          obj, constraints = super(Boolean, self).canonicalize()
          one = lu.create_const(np.ones(self.size), self.size)
          constraints += [lu.create_geq(obj),
                          lu.create_leq(obj, one)]
          return (obj, constraints)
  