zscal

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