zbinu.f

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      SUBROUTINE zbinu(ZR, ZI, FNU, KODE, N, CYR, CYI, NZ, RL, FNUL,
     * tol, elim, alim)
C***BEGIN PROLOGUE  ZBINU
C***REFER TO  ZBESH,ZBESI,ZBESJ,ZBESK,ZAIRY,ZBIRY
C
C     ZBINU COMPUTES THE I FUNCTION IN THE RIGHT HALF Z PLANE
C
C***ROUTINES CALLED  XZABS,ZASYI,ZBUNI,ZMLRI,ZSERI,ZUOIK,ZWRSK
C***END PROLOGUE  ZBINU
      DOUBLE PRECISION ALIM, AZ, CWI, CWR, CYI, CYR, DFNU, ELIM, FNU,
     * fnul, rl, tol, zeroi, zeror, zi, zr, xzabs
      INTEGER I, INW, KODE, N, NLAST, NN, NUI, NW, NZ
      dimension cyr(n), cyi(n), cwr(2), cwi(2)
      DATA zeror,zeroi / 0.0d0, 0.0d0 /
C
      nz = 0
      az = xzabs(zr,zi)
      nn = n
      dfnu = fnu + dble(float(n-1))
      IF (az.LE.2.0d0) go to 10
      IF (az*az*0.25d0.GT.dfnu+1.0d0) go to 20
   10 CONTINUE
C-----------------------------------------------------------------------
C     POWER SERIES
C-----------------------------------------------------------------------
      CALL zseri(zr, zi, fnu, kode, nn, cyr, cyi, nw, tol, elim, alim)
      inw = iabs(nw)
      nz = nz + inw
      nn = nn - inw
      IF (nn.EQ.0) RETURN
      IF (nw.GE.0) go to 120
      dfnu = fnu + dble(float(nn-1))
   20 CONTINUE
      IF (az.LT.rl) go to 40
      IF (dfnu.LE.1.0d0) go to 30
      IF (az+az.LT.dfnu*dfnu) go to 50
C-----------------------------------------------------------------------
C     ASYMPTOTIC EXPANSION FOR LARGE Z
C-----------------------------------------------------------------------
   30 CONTINUE
      CALL zasyi(zr, zi, fnu, kode, nn, cyr, cyi, nw, rl, tol, elim,
     * alim)
      IF (nw.LT.0) go to 130
      go to 120
   40 CONTINUE
      IF (dfnu.LE.1.0d0) go to 70
   50 CONTINUE
C-----------------------------------------------------------------------
C     OVERFLOW AND UNDERFLOW TEST ON I SEQUENCE FOR MILLER ALGORITHM
C-----------------------------------------------------------------------
      CALL zuoik(zr, zi, fnu, kode, 1, nn, cyr, cyi, nw, tol, elim,
     * alim)
      IF (nw.LT.0) go to 130
      nz = nz + nw
      nn = nn - nw
      IF (nn.EQ.0) RETURN
      dfnu = fnu+dble(float(nn-1))
      IF (dfnu.GT.fnul) go to 110
      IF (az.GT.fnul) go to 110
   60 CONTINUE
      IF (az.GT.rl) go to 80
   70 CONTINUE
C-----------------------------------------------------------------------
C     MILLER ALGORITHM NORMALIZED BY THE SERIES
C-----------------------------------------------------------------------
      CALL zmlri(zr, zi, fnu, kode, nn, cyr, cyi, nw, tol)
      IF(nw.LT.0) go to 130
      go to 120
   80 CONTINUE
C-----------------------------------------------------------------------
C     MILLER ALGORITHM NORMALIZED BY THE WRONSKIAN
C-----------------------------------------------------------------------
C-----------------------------------------------------------------------
C     OVERFLOW TEST ON K FUNCTIONS USED IN WRONSKIAN
C-----------------------------------------------------------------------
      CALL zuoik(zr, zi, fnu, kode, 2, 2, cwr, cwi, nw, tol, elim,
     * alim)
      IF (nw.GE.0) go to 100
      nz = nn
      DO 90 i=1,nn
        cyr(i) = zeror
        cyi(i) = zeroi
   90 CONTINUE
      RETURN
  100 CONTINUE
      IF (nw.GT.0) go to 130
      CALL zwrsk(zr, zi, fnu, kode, nn, cyr, cyi, nw, cwr, cwi, tol,
     * elim, alim)
      IF (nw.LT.0) go to 130
      go to 120
  110 CONTINUE
C-----------------------------------------------------------------------
C     INCREMENT FNU+NN-1 UP TO FNUL, COMPUTE AND RECUR BACKWARD
C-----------------------------------------------------------------------
      nui = int(sngl(fnul-dfnu)) + 1
      nui = max0(nui,0)
      CALL zbuni(zr, zi, fnu, kode, nn, cyr, cyi, nw, nui, nlast, fnul,
     * tol, elim, alim)
      IF (nw.LT.0) go to 130
      nz = nz + nw
      IF (nlast.EQ.0) go to 120
      nn = nlast
      go to 60
  120 CONTINUE
      RETURN
  130 CONTINUE
      nz = -1
      IF(nw.EQ.(-2)) nz=-2
      RETURN
      END