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C Copyright (c) 2003-2010 University of Florida
C
C This program is free software; you can redistribute it and/or modify
C it under the terms of the GNU General Public License as published by
C the Free Software Foundation; either version 2 of the License, or
C (at your option) any later version.
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
C GNU General Public License for more details.
C The GNU General Public License is included in this distribution
C in the file COPYRIGHT.
C CALCULATES THE VECTOR V BETWEEN CARTESIAN POINTS A AND B
SUBROUTINE VEC(A,B,V,IX)
IMPLICIT DOUBLE PRECISION (A-H,O-Z)
DIMENSION A(3),B(3),V(3)
V(1)=B(1)-A(1)
V(2)=B(2)-A(2)
V(3)=B(3)-A(3)
C
C This block is added to avoid calling NORMAL when
C the vector is null, Ajith Perera, 10/2010
C
D2 = 0.0D0
Do I = 1, 3
D2 = D2 + V(i)**2
Enddo
D2sqrt = Dsqrt(D2)
If (D2sqrt .LT. 1.0D-14) Then
Write(6,"(a)") "@-VEC: The null vector is returned"
Call Errex
Endif
C
IF(IX.EQ.1)CALL NORMAL(V,3)
RETURN
END
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