subroutine zscal(n,za,zx,incx)
c scales a vector by a constant.
c jack dongarra, 3/11/78.
c modified to correct problem with negative increment,
8/21/90.
double complex za,zx(1)
integer i,incx,ix,n
if(n.le.0)return
if(incx.eq.1)go to 20
c code for increment not equal to 1
ix = 1
if(incx.lt.0)ix = (-n+1)*incx + 1
do 10 i = 1,n
zx(ix) = za*zx(ix)
ix = ix + incx
10 continue
return
c code for increment equal to 1
20 do 30 i = 1,n
zx(i) = za*zx(i)
30 continue
return
end