You might be interested in https://github.com/amalloy/clusp/blob/master/src/snusp/core.clj, my Clojure interpreter for SNUSP (which is brainfuck with different control-flow mechanics). It's purely functional, and IMO does a good job of separating concerns; both of those are things it sounds like you were having trouble with, so hopefully reading it will give you some ideas. Basically my approach is to have an object (hash-map) that represents the state of the interpreter (the "world"), and "compile" each instruction to a function before doing anything. Then, I just look up the instruction at the current position, call it on the world, and use the returned world for the next step.
On Saturday, April 6, 2013 4:49:36 PM UTC-7, Andrew Spano wrote: > > Hello, I'm a new clojure programmer--but after learning a bit of clojure > including iteration, some core high order functions, and a little bit about > state management I decided to try my hand on a brainfuck interpreter. > > Located here: > > https://github.com/recursor94/brainfuck.clj/blob/master/brainfuck/src/brainfuck/fuck.clj > > Handling looping complicated things. And the way I chose to deal with > looping resulted in some pretty ugly functions. I hope to clean that up in > the future and refractor the code into a more functional style after I've > finished the first draft. > > The issue is in a particular function which never stops recuring even when > the condition for recuring is false: > > (defn exec-instruction > "executes each function in the codemap vector in sequential order" > > > ([end-index] > (inc-code-pos) ;;side affect function that moves the code pointer (I > have both a code pointer and a data pointer in my interpreter) > (loop [index (:index @codemap)] > (let [codevec (@codemap :struct) > instruct (get codevec index)] > (println "index:" index > "instruct" instruct > "minus one index:" (- end-index 2)) > (instruct)) > (when-not (= index (- end-index 1)) > (println "yeah you are") > (inc-code-pos) > (recur (inc index))))) > ;;end problem > ([] > (doseq [instruct (@codemap :struct)] > (instruct) ;;higher order functions ftw > (inc-code-pos)))) > > > And here is the function that triggers this function: > > (defn begin-loop > "run through a loop until current cell drops to zero" > [] > (loop [loop-counter (@cells @pointer) > end-loop (find-end (@codemap :index)) ;;find-end returns an integer > pos (@codemap :index)] > (println "cell counter:" loop-counter > "other:" (@cells @pointer) > "at 0:" (@cells @pointer) > "also:" end-loop) ;;debug output > (exec-instruction end-loop) > (when-not (= loop-counter 0) > (recur (@cells @pointer) end-loop pos)))) > > > The program is supposed to stop when it reaches a closing end brace and jump > back to the opening brace in the code. But the output indicates that the > program never gets passed the first iteration. > > For example, given this hello world brainfuck program: > > > ++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>. > > The program outputs the following: > index: 11 instruct #'brainfuck.fuck/+pointer minus one index: 39 > yeah you are > index: 12 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 13 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 14 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 15 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 16 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 17 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 18 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 19 instruct #'brainfuck.fuck/+pointer minus one index: 39 > yeah you are > index: 20 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 21 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 22 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 23 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 24 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 25 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 26 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 27 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 28 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 29 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 30 instruct #'brainfuck.fuck/+pointer minus one index: 39 > yeah you are > index: 31 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 32 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 33 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 34 instruct #'brainfuck.fuck/+pointer minus one index: 39 > yeah you are > index: 35 instruct #'brainfuck.fuck/plus minus one index: 39 > yeah you are > index: 36 instruct #'brainfuck.fuck/-pointer minus one index: 39 > yeah you are > index: 37 instruct #'brainfuck.fuck/-pointer minus one index: 39 > yeah you are > index: 38 instruct #'brainfuck.fuck/-pointer minus one index: 39 > yeah you are > index: 39 instruct #'brainfuck.fuck/-pointer minus one index: 39 > yeah you are > index: 40 instruct #'brainfuck.fuck/minus minus one index: 39 > cell counter: 9 other: 9 at 0: 9 also: 41 > index: 41 instruct #'brainfuck.fuck/end-loop minus one index: 39 > Exception in thread "main" java.lang.IllegalStateException: Attempting to > call unbound fn: #'brainfuck.fuck/end-loop > at clojure.lang.Var$Unbound.throwArity(Var.java:43) > at clojure.lang.AFn.invoke(AFn.java:35) > at clojure.lang.Var.invoke(Var.java:411) > at brainfuck.fuck$exec_instruction.invoke(fuck.clj:142) > at brainfuck.fuck$begin_loop.invoke(fuck.clj:94) > at clojure.lang.Var.invoke(Var.java:411) > at brainfuck.fuck$exec_instruction.invoke(fuck.clj:149) > at brainfuck.fuck$_main.invoke(fuck.clj:165) > at clojure.lang.Var.invoke(Var.java:411) > at user$eval218.invoke(NO_SOURCE_FILE:1) > at clojure.lang.Compiler.eval(Compiler.java:6511) > at clojure.lang.Compiler.eval(Compiler.java:6501) > at clojure.lang.Compiler.eval(Compiler.java:6477) > at clojure.core$eval.invoke(core.clj:2797) > at clojure.main$eval_opt.invoke(main.clj:297) > at clojure.main$initialize.invoke(main.clj:316) > at clojure.main$null_opt.invoke(main.clj:349) > at clojure.main$main.doInvoke(main.clj:427) > at clojure.lang.RestFn.invoke(RestFn.java:421) > at clojure.lang.Var.invoke(Var.java:419) > at clojure.lang.AFn.applyToHelper(AFn.java:163) > at clojure.lang.Var.applyTo(Var.java:532) > at clojure.main.main(main.java:37) > > > Aside from too much incidental complexity, I can't figure out what I did > wrong here and why the loop never seems to stop iterating when it clearly > should. Any help at all is sincerely appreciated. In fact, I'd love any > pointers about the program structure itself if you care to take a look at my > github. > > Thanks, > > --Andrew > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
