joyofclojure

Streams were equipped with plus and bind, I removed bind and added join and narrow.
I also added yield which returns the yielded substitution map for the stream (if any) 
and step which advances teh computation (was: calling the thunk).

join, like plus, interleaves execution of its two streams. As soon as one yields, the
yielded value is used to narrow the search space of the other stream.

For any stream A, we have:
  A = (plus (yield A) (step A))

joyofclojure

#!/usr/bin/env ruby

class MRISC
  def run(code)
    tokens = code.gsub(/(\*.*?\*)|[^a-z0-9,-;@\._]/,'').split(';')
    @vars,stack,i = {:_pc=>-1,:_oc=>0},[],0
    tokens.map!{|t| t.chars.first=='@' ? (@vars[t.to_sym]=i-1;nil) : (i+=1;t.split(',').map{|e|numeric?(e) ? e.to_i : e.to_sym})}.compact!
    while @vars[:_pc] < tokens.size-1
      @vars[:_pc] += 1
      @vars[:_oc] += 1