<div dir="ltr">If you were to replace stream-cons with this function:<div><br></div><div>(define (not-stream-cons x y) (printf "x ~s y ~s\n" x y) 'something-random)</div><div><br></div><div>would it make sense to you what happens?</div> <div><br></div><div>Robby</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, May 16, 2013 at 7:30 AM, Patrick Sweetman <span dir="ltr"><<a href="mailto:sweetmanpc@woosh.co.nz" target="_blank">sweetmanpc@woosh.co.nz</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I'm doing this problem:<br> <br> 6. Write a stream dan-then-dog, where the elements of the stream<br> alternate between the strings "dan.jpg" and "dog.jpg" (starting with<br> "dan.jpg"). More specically, dan-then-dog should be a thunk that when<br> called produces a pair of "dan.jpg" and a thunk that when called<br> produces a pair of "dog.jpg" and a thunk that when called... etc. Sample<br> solution: 4 lines.<br> <br> and I cannot for the life of me understand why the following code does<br> not produce a properly thunked stream. It evaluates the entries until it<br> runs out of memory<br> <br> (define dan "dan.jpg")<br> (define dog "dog.jpg")<br> <br> (define (dan-then-dog)<br> (define (H1 st0 b0)<br> (cond<br> [(= b0 1) (H1 (stream-cons dan st0) 0)]<br> [else (H1 (stream-cons dog st0) 1)]<br> )<br> )<br> (H1 empty-stream 1))<br> <br> Can somebody please explain why my understanding of Racket streams is<br> faulty?<br> <br> Thanks,<br> Patrick Sweetman<br> ____________________<br> Racket Users list:<br> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a><br> </blockquote></div><br></div>