#-------------------------------------------------------------
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you 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.
#
#-------------------------------------------------------------

# Builtin function that implements unique operation on vectors
#
# INPUT:
# -------------------------------------------------------
# X     input vector
# -------------------------------------------------------
#
# OUTPUT:
# -------------------------------------------------------------------
# R     matrix with only unique rows
# -------------------------------------------------------------------

m_unique = function(matrix[double] X)
  return (matrix[double] R)
{
  R = X
  if(nrow(X) > 1) {
    # sort-based approach (a generic alternative would be transformencode)
    X_sorted = order(target=X, by=1, decreasing=FALSE, index.return=FALSE);
    temp = X_sorted[1:nrow(X_sorted)-1,] != X_sorted[2:nrow(X_sorted),];
    mask = rbind(matrix(1, 1, 1), temp);
    R = removeEmpty(target = X_sorted, margin = "rows", select = mask);
  }
}
