float a
float b
float c
float d

float x
float y
float dx
float dy

proc init
  2.0 a f!
  1.0 b f!
  2.0 c f!
  8.0 d f!

  1.0 x f!
  2.0 y f!
endproc

init

float delta
1.0e-4 delta f!

proc step-solve
  a f@ x f@ f*
  b f@ x f@ f* y f@ f* f-
  dx f!
  c f@ x f@ f* y f@ f*
  d f@ y f@ f* f-
  dy f!

  dx f@ delta f@ f* x f@ f+ x f!
  dy f@ delta f@ f* y f@ f+ y f!
endproc

0 chart.show
0 chart.align.client

0 0 chart.addseries
1 0 chart.addseries

0x003f3F 0 SERIES.COLOR
0xFF3F00 1 SERIES.COLOR

int steps
int #series

proc run
  init
  #series series.clear
  steps 0 do
    step-solve
    x f@ y f@ #series series.fxy
  loop
endproc

0 to #series
10000 to steps
1.0e-3 delta f!
run

1 to #series
100000 to steps
1.0e-4 delta f!
run