X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment8.mdwn;h=cdb32e875beaa8cbab5f6e2171ce08f6814ae62e;hp=abc14d08b87337bbaa56a1d025157714a0c6949a;hb=3c9d5a19d05c749c3bf4e05874bcb153db3a18c6;hpb=94d8065f557f70e448841089c6860e208fed55f6 diff --git a/assignment8.mdwn b/assignment8.mdwn index abc14d08..cdb32e87 100644 --- a/assignment8.mdwn +++ b/assignment8.mdwn @@ -83,17 +83,18 @@ Some other Scheme details: * `#t` is true and `#f` is false + * `(lambda () ...)` constructs a thunk + * there is no difference in meaning between `[...]` and `(...)`; we just sometimes use the square brackets for clarity * `'(1 . 2)` and `(cons 1 2)` are pairs (the same pair) * `(list)` and `'()` both evaluate to the empty list * `(null? lst)` tests whether `lst` is the empty list * non-empty lists are implemented as pairs whose second member is a list - * `'() '(1) '(1 2) '(1 2 3) are all lists - * `(list)` `(list1)` `(list 1 2)` `(list 1 2 3)` are the same lists - * `'(1 2 3)` and `(cons 1 '(2 3))` are pairs that are also lists (the same list) + * `'()` `'(1)` `'(1 2)` `'(1 2 3)` are all lists + * `(list)` `(list 1)` `(list 1 2)` `(list 1 2 3)` are the same lists + * `'(1 2 3)` and `(cons 1 '(2 3))` are both pairs and lists (the same list) * `(pair? lst)` tests whether `lst` is a pair; if `lst` is a non-empty list, it will also pass this test; if `lst` fails this test, it may be because `lst` is the empty list, or because it's not a list or pair at all * `(car lst)` extracts the first member of a pair / head of a list * `(cdr lst)` extracts the second member of a pair / tail of a list - * `(lambda () ...)` constructs a thunk Here is the implementation: