You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
11 lines
645 B
11 lines
645 B
|
|
Exercise 4.26: Ben Bitdiddle and Alyssa
|
|
P. Hacker disagree over the importance of lazy evaluation for implementing
|
|
things such as unless. Ben points out that it’s possible to implement
|
|
unless in applicative order as a special form. Alyssa counters that, if
|
|
one did that, unless would be merely syntax, not a procedure that could
|
|
be used in conjunction with higher-order procedures. Fill in the details on
|
|
both sides of the argument. Show how to implement unless as a derived
|
|
expression (like cond or let), and give an example of a situation
|
|
where it might be useful to have unless available as a procedure, rather
|
|
than as a special form.
|
|
|