I see that some Matthew gave you a fish and William sketched how Matthew may have caught the fish. Here is a fishing net
http://www.ccs.neu.edu/home/matthias/HtDP2e/part_four.html#%28part._ch~3asimu%29 <http://www.ccs.neu.edu/home/matthias/HtDP2e/part_four.html#(part._ch~3asimu)> It comes with instructions on how to fish. > On Apr 15, 2017, at 10:16 AM, Angus <[email protected]> wrote: > > I have a function that can return either false or a node. I have to check > four permutations: > > both nodes false, > left node false, > right node valid, left node false > both node valid > > I am doing it using cond like this: > > (define (lines t) > (cond [(and (false? (node-l t)) (false? (node-r t))) <<do no children > thing>>] ;; if no children > [(and (false? (node-l t)) (not (node-r t))) <<left child only>>] ;; > if left child only > [(and (node-l t) (false? (node-r t))) <<right child only>> ] ;; if > right child only > [else <<both children>> ])) ;; if both children > > > the first cond line using and and false? works ok and the last cond line > using else works ok. But how do I check for the middle two occurrences? > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
