Category : Miscellaneous Language Source Code
Archive   : FORTRN77.ZIP
Filename : NAREGU.FOR

 
Output of file : NAREGU.FOR contained in archive : FORTRN77.ZIP
SUBROUTINE NAREGU(XLOW,XHI,EPS,ROOT,N)
C
C THIS SUBROUTINE FINDS THE ROOT OF THE EQUATION F(X) = 0
C THROUGH THE METHOD OF FALSE POSITION(REGULA FALSI).
C
NMAX = N
N = 0
CALL VALUE(XHI,FXHI)
CALL VALUE(XLOW,FXLOW)
IF(FXHI.GE.0.0) GO TO 20
XP = XLOW
FXP = FXLOW
XQ = XHI
FXQ = FXHI
GO TO 7
20 XP = XHI
FXP = FXHI
XQ = XLOW
FXQ = FXLOW
7 XNEW = XP - FXP*(XP - XQ)/(FXP - FXQ)
CALL VALUE(XNEW,FXNEW)
N = N + 1
IF(ABS(FXNEW).GT.EPS) GO TO 2
ROOT = XNEW
N = 1
RETURN
2 IF(N.LT.NMAX) GO TO 40
ROOT = XNEW
N = 2
RETURN
40 IF(FXNEW.GT.0.0) GO TO 4
X = XNEW - FXNEW*(XNEW-XQ)/(FXNEW - FXQ)
XQ = XNEW
FXQ = FXNEW
15 IF(XP.LE.XQ) GO TO 6
IF(XP.LE.X) GO TO 7
IF(X.LE.XQ) GO TO 7
9 N = N + 1
CALL VALUE(X,FX)
IF(ABS(FX).GT.EPS) GO TO 17
ROOT = X
N = 1
RETURN
17 IF(N.LT.NMAX) GO TO 18
ROOT = X
N = 2
RETURN
18 IF(FX.GT.0.0) GO TO 11
XQ = X
FXQ = FX
GO TO 7
11 XP = X
FXP = FX
GO TO 7
6 IF(XQ.LE.X) GO TO 7
IF(X.LE.XP) GO TO 7
GO TO 9
4 X = XNEW - FXNEW*(XNEW - XP)/(FXNEW - FXP)
XP = XNEW
FXP = FXNEW
GO TO 15
RETURN
END



  3 Responses to “Category : Miscellaneous Language Source Code
Archive   : FORTRN77.ZIP
Filename : NAREGU.FOR

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/