apply_sigmoid Function

  function apply_sigmoid(this, val) result(output)
    !! Apply sigmoid activation to 1D array
    !!
    !! Computes: f = 1/(1+exp(-x))
    implicit none

    ! Arguments
    class(sigmoid_actv_type), intent(in) :: this
    !! Sigmoid activation type
    type(array_type), intent(in) :: val
    !! Input values
    type(array_type), pointer :: output
    !! Activated output values in range [0,1]

    if(this%apply_scaling)then
       output => sigmoid(val) * this%scale
    else
       output => sigmoid(val)
    end if
  end function apply_sigmoid