Re: Continuations

On Sat, 13 Jul 2024 23:43:52 -0000 (UTC), Lawrence D'Oliveiro
<ldo@nz.invalid> wrote:

On Sat, 13 Jul 2024 17:42 +0100 (BST), John Dallman wrote:
>

In article <v6tbki$3g9rg$1@dont-email.me>, ldo@nz.invalid (Lawrence
D'Oliveiro) wrote:
 

The beauty of continuations is that they are a single generalized
control construct that can be used to implement specific language
features like regular routine calls, loops, exceptions and coroutines,
all built from the same common abstraction. One thing that is difficult
to do with them is arbitrary gotos. (I consider that a feature, not a
bug.)

 
Just occasionally, you need a goto to get out of a complicated error
situation. Not often, but sometimes.

>
That’s what exceptions are for. And they are handled by continuations as
well.

At its simplest, a continuation is simply "the next instruction to be
executed", so any time you take/save a code address and then jump to
it you have executed a continuation.

Many languages permit "callbacks", which are a form of continuation. 

The notion of "continuation" in Lisp has been conflated with function
calling.  Continuations which take/permit arguments are a particularly
heavyweight form.