quadct.for

Numerical Recipes一书中例子的源码所用到的函数集,William H. Press 和 Saul A. Teukolsky 所著

      SUBROUTINE quadct(x,y,xx,yy,nn,fa,fb,fc,fd)
      INTEGER nn
      REAL fa,fb,fc,fd,x,y,xx(nn),yy(nn)
      INTEGER k,na,nb,nc,nd
      REAL ff
      na=0
      nb=0
      nc=0
      nd=0
      do 11 k=1,nn
        if(yy(k).gt.y)then
          if(xx(k).gt.x)then
            na=na+1
          else
            nb=nb+1
          endif
        else
          if(xx(k).gt.x)then
            nd=nd+1
          else
            nc=nc+1
          endif
        endif
11    continue
      ff=1.0/nn
      fa=ff*na
      fb=ff*nb
      fc=ff*nc
      fd=ff*nd
      return
      END