From 7dfcc480ba1e19bd3232349fc733caef94034292 Mon Sep 17 00:00:00 2001
From: stainer_t <thomas.stainer@oecd-nea.org>
Date: Mon, 8 Sep 2025 13:48:49 +0200
Subject: Initial commit from Polytechnique Montreal

---
 Dragon/src/NXTTRS.f | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 Dragon/src/NXTTRS.f

(limited to 'Dragon/src/NXTTRS.f')

diff --git a/Dragon/src/NXTTRS.f b/Dragon/src/NXTTRS.f
new file mode 100644
index 0000000..1beba30
--- /dev/null
+++ b/Dragon/src/NXTTRS.f
@@ -0,0 +1,83 @@
+*DECK NXTTRS
+      FUNCTION NXTTRS(ITRCUR,ISYM)
+*
+*----------
+*
+*Purpose:
+* Find new DRAGON TURN factor associated after a Cartesian symmetry
+* is applied on an old DRAGON TURN factor.
+*
+*Copyright:
+* Copyright (C) 2004 Ecole Polytechnique de Montreal
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License as published by the Free Software Foundation; either
+* version 2.1 of the License, or (at your option) any later version.
+*
+*Author(s): G. Marleau.
+*
+*Parameters: input
+* ITRCUR  initial turn factor.
+* ISYM    symmetry to consider where:
+*         =-1 indicates $Z$ reflection symmetry;
+*         = 1 indicates $X$ reflection symmetry;
+*         = 2 indicates $X=Y$ diagonal symmetry;
+*         = 3 indicates $Y$ reflection symmetry;
+*         = 4 indicates $X=-Y$ diagonal symmetry.
+*
+*Parameters: output
+* NXTTRS  turn factor after symmetry is applied.
+*
+*----
+      IMPLICIT         NONE
+*----
+*  Subroutine arguments
+*----
+      INTEGER          ITRCUR,ISYM
+      INTEGER          NXTTRS
+*----
+*  Local parameters
+*----
+      INTEGER          IOUT
+      CHARACTER        NAMSBR*6
+      PARAMETER       (IOUT=6,NAMSBR='NXTTRS')
+      INTEGER          MAXTUR
+      PARAMETER       (MAXTUR=12)
+*----
+*  Local variables
+*----
+      INTEGER          ISZ,ICTP,IRTR
+*----
+*  Test input data
+*  ITRCUR can be 1-8 or 13-20
+*  ISYM can be 1-4
+*----
+      IF((ITRCUR .LE.  0) .OR.
+     >   (ITRCUR .GE.  9 .AND. ITRCUR .LE. 12) .OR.
+     >   (ITRCUR .GE. 21)) CALL XABORT(NAMSBR//
+     >  ': Invalid TURN')
+      IF(ISYM .LT. -1 .OR.
+     >   ISYM .EQ.  0 .OR.
+     >   ISYM .GT. 4 ) CALL XABORT(NAMSBR//
+     >  ': Invalid symmetry')
+*----
+*  Find current symmetry factor in Z (ISZ) and current turn
+*  number in plane X-Y (ICTP)
+*----
+      ISZ=((ITRCUR-1)/MAXTUR)
+      ICTP=MOD(ITRCUR-1,MAXTUR)+1
+      IF(ISYM .EQ. -1) THEN
+*----
+*  Z symmetry
+*----
+        ISZ=(1-ISZ)
+      ELSE
+*----
+*  X, X-Y AND Y symmetry
+*----
+        IRTR=((ICTP-1)/4)*4
+        ICTP=MOD(4-ICTP+IRTR+ISYM,4)+5-IRTR
+      ENDIF
+      NXTTRS=ICTP+MAXTUR*ISZ
+      RETURN
+      END
-- 
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