Resource:
http://en.wikibooks.org/wiki/Haskell/Continuation_passing_style
http://mainline.brynmawr.edu/cs245/cps.pdf
http://en.wikipedia.org/wiki/Continuation-passing_style
Definition:
Continuation Passing Style is a formed for expressions such that no function ever returns, instead they pass control onto a continuation.
or,
"A data structure represents what is left to do."
Features:
- return early
- exceptions and failure can be signalled
- pass in a continuation for success
- pass in another continuation for fail
- suspend
Why:
- CPS quickly fills the stack or has to be given hand-coded infrastructure in languages that don't support the automatic merging of unneeded stack frames.
To Complement:
- every function takes an extra argument, its continuation
- every argument in a function call must be either a variable or a lambda expression (not a more complex expression)
Note:
- There's no implicit continuation - every call is a tail call.
- There's no magic there, every continuation is simply explicitly passed.
- For using CPS without tail call optimisation will cause not only the constructed continuation potentially grow during recursion, but also the call stack.
Another Topic, Call-with-current-continuation:
- Scheme allows the continuation of a computation to be captured by call/cc.
- (call/cc proc), where proc is a one-parameter function.
- (define get-back 'any), usage: (get-back k)
- (exit 0), escaping from deep recursion.
My Review:
Quite hard to read Scheme code especially with lots for function calls and recursion. This might because I am more familiar with basic imperative programming languages.
