id = 176
name = 'algol/3'
slug = 'interpreter for mini-algol'

description = '''\
<p>A DCG for mini-algol.</p>
<pre>
  % apply a function to a starting state
  ?- apply([a=2], Out, fun(_In, Out, eval(a+3, _In, Out))).
    Out = 5.

  % a := a+b
  % b := a-b
  % a := a-b
  ?- _Program = [begin,a,:=,a+b,b,:=,a-b,a,:=,a-b,end],
      algol(_F, _Program, []),
      apply([a=3,b=5], Output, _F).
    Output = [a=5,b=3,printout=[]].

  % a := 0
  % while a < 10 do
  % begin
  %   print(a)
  %   a := a+1
  % end
  ?- _Program = [begin,a,:=,0,while,a,<,10,do,begin,print(a),a,:=,a+1,end,end],
      algol(_F, _Program, []),
      apply([a=3], Output, _F).
    Output = [a=10,printout=[0,1,2,3,4,5,6,7,8,9]].
</pre>
'''

hint = {}