! Molecular Orbital PACkage (MOPAC)
! Copyright 2021 Virginia Polytechnic Institute and State University
!
! 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.

      double precision function dot (x, y, n)
!-----------------------------------------------
!   M o d u l e s
!-----------------------------------------------
      implicit none
!-----------------------------------------------
!   D u m m y   A r g u m e n t s
!-----------------------------------------------
      integer , intent(in) :: n
      double precision , intent(in) :: x(n)
      double precision , intent(in) :: y(n)
!For MOPAC BLAS
      double precision, external :: ddot
!

!-----------------------------------------------
!***********************************************************************
!
!   DOT FORMS THE SCALAR PRODUCT OF TWO VECTORS.
!
!   ON INPUT     X   =    FIRST VECTOR, OF LENGTH N.
!                Y   =    SECOND VECTOR, OF LENGTH N.
!
!   ON RETURN    DOT =    DOT PRODUCT OF X AND Y.
!
!***********************************************************************
!For MOPAC BLAS
!     dot = dot_product(x(:n),y(:n))
      dot = ddot(n,x(1:n),1,y(1:n),1)
!
      return
      end function dot
