! Decay, version 1.
! Ian R. Gatland, initiated 1997/08/11, last updated 1998/05/21.
! Based on "Decay" in "Computational Physics" by N. Giordano.
program Decay1
   library "IrGraphics*"
   option nolet
   id$ = "IRG: Decay1"
   dim t(0), n(0)
   call Init(nt, dt, t0, n0, r)
   mat redim t(0:nt), n(0:nt)
   t(0) = t0
   n(0) = n0
   call Calc(nt, dt, t(), n(), r)
   call Graph1A(id$, "time", "number", t(), n(), 1)
   print " t = "; t(nt)
   print " n = "; n(nt)
   print "Done"
end
sub Init(nt, dt, t0, n0, r)
   nt = 100           ! number of time steps
   dt = 0.01          ! time step
   t0 = 0             ! initial time
   n0 = 1             ! initial value
   r = 3              ! decay rate
end sub
sub Calc(nt, dt, t(), n(), r)
   for i = 1 to nt
      nd = - r*n(i-1)
      t(i) = t(i-1) + dt
      n(i) = n(i-1) + nd*dt
   next i
end sub