The fundamental concept of continuations
see at sig.below
Tue Oct 9 07:59:28 CEST 2007
In article <1191906949.179197.217470 at 57g2000hsv.googlegroups.com>,
gnuist006 at gmail.com wrote:
> Again I am depressed to encounter a fundamentally new concept that I
> was all along unheard of.
Don't be depressed about that. There are countless concepts out there
they you haven't yet heard of.
> Its not even in paul graham's book where i
> learnt part of Lisp. Its in Marc Feeley's video.
> Can anyone explain:
> (1) its origin
Lambda calculus. Instead of function A returning to its caller, the
caller provides an additional argument (the "continuation") which is a
function B to be called by A with A's result(s). In pure "continuation
style" coding, nothing ever "returns" a result.
It is easy to mechanically transform normal function-style lambda
calculus into continuation-style, but the reverse is not so.
> (2) its syntax and semantics in emacs lisp, common lisp, scheme
> (3) Is it present in python and java ?
Java, sort of. For example, the Run interface.
Python, I don't know.
> (4) Its implementation in assembly. for example in the manner that
> pointer fundamentally arises from indirect addressing and nothing new.
> So how do you juggle PC to do it.
You can have a "spaghetti stack", or keep continuation data-structures
in the heap.
> (5) how does it compare to and superior to a function or subroutine
> call. how does it differ.
This sounds like homework. What do you have so far?
> Thanks a lot.
> (6) any good readable references that explain it lucidly ?
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