X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?a=blobdiff_plain;f=from_lists_to_continuations.mdwn;h=c67d5e86c173063a1c7c455b9ada08ea09ad373c;hb=13d59901132acc7a49220d84363227d2f7d1f476;hp=f2e6989d14e362e2f9b10e2c5d5d07b08da49ae7;hpb=db72ac41480e82e56a4ac35fc2d710d610200486;p=lambda.git diff --git a/from_lists_to_continuations.mdwn b/from_lists_to_continuations.mdwn index f2e6989d..c67d5e86 100644 --- a/from_lists_to_continuations.mdwn +++ b/from_lists_to_continuations.mdwn @@ -6,7 +6,7 @@ to continuations is to re-functionalize a zipper. Then the concreteness and understandability of the zipper provides a way of understanding and equivalent treatment using continuations. -Let's work with lists of chars for a change. To maximize readability, we'll +Let's work with lists of `char`s for a change. To maximize readability, we'll indulge in an abbreviatory convention that "abSd" abbreviates the list `['a'; 'b'; 'S'; 'd']`. @@ -75,9 +75,9 @@ guarantees termination, and a final string without any `'S'` in it. This is a task well-suited to using a zipper. We'll define a function `tz` (for task with zippers), which accomplishes the task by mapping a -char list zipper to a char list. We'll call the two parts of the +`char list zipper` to a `char list`. We'll call the two parts of the zipper `unzipped` and `zipped`; we start with a fully zipped list, and -move elements to the zipped part by pulling the zipped down until the +move elements to the zipped part by pulling the zipper down until the entire list has been unzipped (and so the zipped half of the zipper is empty).
@@ -131,8 +131,8 @@ to get there, we'll first do the exact same thing we just did with concrete zipper using procedures. Think of a list as a procedural recipe: `['a'; 'b'; 'S'; 'd']` -is the result of the computation `a::(b::(S::(d::[])))` (or, in our old -style, `makelist a (makelist b (makelist S (makelist c empty)))`). +is the result of the computation `'a'::('b'::('S'::('d'::[])))` (or, in our old +style, `make_list 'a' (make_list 'b' (make_list 'S' (make_list 'd' empty)))`). The recipe for constructing the list goes like this:@@ -151,10 +151,10 @@ be a function of type `char list -> char list`. We'll call each step context, a continuation is a function of type `char list -> char list`. For instance, the continuation corresponding to the portion of the recipe below the horizontal line is the function `fun (tail:char -list) -> a::(b::tail)`. +list) -> 'a'::('b'::tail)`. This means that we can now represent the unzipped part of our -zipper--the part we've already unzipped--as a continuation: a function +zipper---the part we've already unzipped---as a continuation: a function describing how to finish building the list. We'll write a new function, `tc` (for task with continuations), that will take an input list (not a zipper!) and a continuation and return a processed list.