xrng4.f

24 lines · 1 definitions · on GitHub (7be4133)

Python version: xrng4.py, 29 lines, on the right (switch to Python above the code).

Purpose

XRNG4 chooses four consecutive table indices around index JX in a table of NUMX entries, for 4-point interpolation: JX1 to JX2 = JX-1 to JX+2, shifted to 1..4 near the start and to NUMX-3..NUMX near the end.

How it fits

Called only by GTPURZ, the pure-Z opacity table's interpolation (GTLAOL and GTLAOL2, which also called it, are removed since rp_1 with the LAOL89 tables). No COMMON blocks.

Definitions

subroutineXRNG4

lines 5–24 · GitHub

Four consecutive indices around JX, kept inside 1..NUMX.

Called by GTPURZ

Change log

The changes since rp_1

Changed since rp_1. Declarations only: IMPLICIT NONE; its other callers, GTLAOL and GTLAOL2, are removed.

1 2CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC 3C GET FOUR POINTS IN X ARRAY WHICH SURROUND X 4CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC 5 SUBROUTINE XRNG4(JX,NUMX,JX1,JX2) 6C 10/20/26 MHP via Claude 7C code changed to replace implicit typing with IMPLICIT NONE and 8C explicit declarations. 9 IMPLICIT NONE 10 INTEGER JX,JX1,JX2,NUMX 11 save 12 13 IF (JX.LE.2) THEN 14 JX1 = 1 15 JX2 = 4 16 ELSE IF (JX.GE.NUMX-2) THEN 17 JX1 = NUMX-3 18 JX2 = NUMX 19 ELSE 20 JX1 = JX - 1 21 JX2 = JX + 2 22 END IF 23 RETURN 24 END

1"""Python version of xrng4.f (YREC 7be4133): four consecutive table 2indices around an index, for 4-point interpolation.""" 3 4 5def xrng4(jx: int, numx: int, jx1: int, jx2: int) -> tuple[int, int]: 6 """Choose four consecutive indices jx1..jx2 around jx (jx-1..jx+2), 7 shifted to 1..4 near the start and numx-3..numx near the end. 8 9 Translates: xrng4.f#XRNG4 (7be4133) 10 11 Arguments: jx, the index; numx, the table's length; jx1 and jx2 are 12 passed in with any value. 13 14 Returns (jx1, jx2). 15 16 """ 17 18 # Question (see the page): numx < 4 gives indices outside the table. 19 # The four indices (Fortran lines 13–22). 20 if jx <= 2: 21 jx1 = 1 22 jx2 = 4 23 elif jx >= numx - 2: 24 jx1 = numx - 3 25 jx2 = numx 26 else: 27 jx1 = jx - 1 28 jx2 = jx + 2 29 return jx1, jx2