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130 lines
3.9 KiB
130 lines
3.9 KiB
c ------------------------------------------------
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double complex function HPL2ar1(n1,n2,x)
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implicit none
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integer n1,n2,j,bcflag
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double complex x,ris,myi,zp,llzp
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double precision pi, zeta2,ll2,xre
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pi=3.1415926535897932385D0
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zeta2=pi**2/6d0
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myi = dcmplx(0d0,1d0)
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ll2 = dlog(2d0)
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bcflag = 0
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j=1+(n2+1)+(n1+1)*3
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ris = dcmplx(0d0,0d0)
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c--- +i*epsilon to get branch cuts right ---
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if (dimag(x).eq.0d0) then
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x = x + dcmplx(0d0,1d-60)
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bcflag = 1
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endif
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c---
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select case(j)
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case(1) !-1-1
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zp = 1d0-x
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ris = -((zp*ll2)/2d0) + (ll2**2)/2d0 + zp**
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& 5*(5d0/384d0 - (ll2)/160d0) + zp**3*(1d0/16d0 - (ll2)/2
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& 4d0) + zp**6*(137d0/23040d0 - (ll2)/384d0) + zp**4*(11d
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& 0/384d0 - (ll2)/64d0) + zp**2*(1d0/8d0 - (ll2)/8d0)
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case(2) !-10
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zp = 1d0-x
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ris = -((pi**2)/12d0) + (zp**2)/4d0 + (zp**
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& 3)/6d0 + (5d0*zp**4)/48d0 + (zp**5)/15d0 + (2d0*zp**6)/
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& 45d0
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case(3) !-11
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zp = 1d0-x
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llzp = log(zp)
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ris = (pi**2)/12d0 - (ll2**2)/2d0 + zp**5*(
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& -(1d0/800d0) + (llzp)/160d0) + zp**3*(-(1d0/72d0) + (ll
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& zp)/24d0) + zp*(-(1d0/2d0) + (llzp)/2d0) + zp**6*(-(1d0
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& /2304d0) + (llzp)/384d0) + zp**4*(-(1d0/256d0) + (llzp)
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& /64d0) + zp**2*(-(1d0/16d0) + (llzp)/8d0)
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case(4) !0-1
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zp = 1d0-x
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ris = (pi**2)/12d0 - zp*ll2 + zp**2*(1d0/4d
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& 0 - (ll2)/2d0) + zp**3*(5d0/24d0 - (ll2)/3d0) + zp**4*(
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& 1d0/6d0 - (ll2)/4d0) + zp**5*(131d0/960d0 - (ll2)/5d0)
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& + zp**6*(661d0/5760d0 - (ll2)/6d0)
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case(5) !00
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zp = 1d0-x
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ris = (zp**2)/2d0 + (zp**3)/2d0 + (11d0*zp*
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& *4)/24d0 + (5d0*zp**5)/12d0 + (137d0*zp**6)/360d0
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case(6) !01
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zp = 1d0-x
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llzp = log(zp)
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ris = (pi**2)/6d0 + zp*(-1 + llzp) + zp**2*
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& (-(1d0/4d0) + (llzp)/2d0) + zp**3*(-(1d0/9d0) + (llzp)/
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& 3d0) + zp**4*(-(1d0/16d0) + (llzp)/4d0) + zp**5*(-(1d0/
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& 25d0) + (llzp)/5d0) + zp**6*(-(1d0/36d0) + (llzp)/6d0)
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case(7) !1-1
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zp = 1d0-x
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llzp = log(zp)
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ris = -((pi**2)/12d0) + (zp)/2d0 + (zp**2)/
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& 16d0 + (zp**3)/72d0 + (zp**4)/256d0 + (zp**5)/800d0 + (
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& zp**6)/2304d0 + (ll2**2)/2d0 - ll2*llzp
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case(8) !10
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zp = 1d0-x
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ris = -((pi**2)/6d0) + zp + (zp**2)/4d0 + (
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& zp**3)/9d0 + (zp**4)/16d0 + (zp**5)/25d0 + (zp**6)/36d0
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case(9) !11
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zp = 1d0-x
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llzp = log(zp)
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ris = (llzp**2)/2d0
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c End of expansions around x = +1
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end select
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c --- set the imaginary part back to zero if it has been modified to
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c --- get the branch cuts right (and should be zero).
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if (bcflag.eq.1) then
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xre = dreal(x)
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if (n2.eq.0.and.xre.gt.0d0) then
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if (xre.lt.1d0) then
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ris = dcmplx(dreal(ris),0d0)
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endif
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c
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else if (n2.eq.1.and.xre.lt.1d0) then
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if (n1.ne.-1) then
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ris = dcmplx(dreal(ris),0d0)
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else if (xre.gt.-1d0) then
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ris = dcmplx(dreal(ris),0d0)
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endif
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c
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else if (n2.eq.-1.and.xre.gt.-1d0) then
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if (n1.ne.1) then
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ris = dcmplx(dreal(ris),0d0)
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else if (xre.lt.1d0) then
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ris = dcmplx(dreal(ris),0d0)
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endif
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endif
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endif
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HPL2ar1=ris
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return
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end function
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