Primitive 'trace'

It is possible so as to follow the working of a program to have it show the procedures which are working. This mode equally allows to show if the procedures provide arguments thanks to the primitive output. To operate this mode, you type:

trace

stoptrace will disactivate the "trace" mode. A small example with the factorial (see page ).

trace pr fac 4
fac 4
  fac 3
    fac 2
      fac 1
      fac returns 1
    fac returns 2
  fac returns 6
fac returns 24
24