Editing Continuation (section)

=== Helpful metaphors, images ===

Here is a collection of short descriptions, analogies or metaphors, that illustrate this difficult concept, or an aspect of it.

==== Imperative metaphors ====

* In computing, a continuation is a representation of the execution state of a program (for example, the call stack) at a certain point in time (Wikipedia's [http://en.wikipedia.org/wiki/Continuation Continuation]).
*  At its heart, <code>call/cc</code> is something like the <code>goto</code> instruction (or rather, like a label for a <code>goto</code> instruction); but a Grand High Exalted <code>goto</code> instruction... The point about <code>call/cc</code> is that it is not a ''static'' (lexical) <code>goto</code> instruction but a ''dynamic'' one (David Madore's [http://www.madore.org/~david/computers/callcc.html#sec_intro A page about <code>call/cc</code>])

==== Functional metaphors ====

* Continuations represent the future of a computation, as a function from an intermediate result to the final result ([http://www.haskell.org/haskellwiki/All_About_Monads#The_Continuation_monad] section in Jeff Newbern's All About Monads)
* The idea behind CPS is to pass around as a function argument what to do next ([http://users.umiacs.umd.edu/~hal/docs/daume02yaht.pdf Yet Another Haskell Tutorial] written by Hal Daume III, 4.6 Continuation Passing Style, pp 53-56. It can also be read in [http://en.wikibooks.org/wiki/Haskell/YAHT/Type_basics#Continuation_Passing_Style wikified format]).
* Rather than return the result of a function, pass one or more [[Higher order function | Higher Order Functions]] to determine what to do with the result. Yes, direct sum like things (or in generally, case analysis, managing cases, alternatives) can be implemented in CPS by passing ''more'' continuations.