Re: Syntax-rules generate symbol

[Taylan Ulrich B.]

Panicz Maciej Godek <address@hidden> writes:

> I assume that the main reason for using this is efficiency (rather
> than simplicity), because allegedly guile's continuations are rather
> inefficient.
>
> On one hand, it's good to know that (and would be even better
> to be able to find it out by skimming section 6.13 of the manual),
> but on the other it would be nicer if the compiler could trace the
> usages of continuations and figure out whether a given one is
> ever being re-entered, and optimize accordingly.

Delimited/composable continuations don't have the efficiency problems of
call/cc (some of which are inherent, and not related to Guile, from what
I know), and I'd urge anyone to read the following critique of call/cc
revealing other problems with it as well. :)

http://okmij.org/ftp/continuations/against-callcc.html

Guile supports "prompts" as the primitive behind higher-level delimited
continuation operators, escape continuations, exceptions, etc.  The
relevant manual section is a nice read, though it might require more
than a quick skim:  (info "(guile) Prompts")

The compiler might be able to optimize some usages of call/cc into the
more efficient use of a delimited continuation, but after reading about
call/cc and delimited continuations, it becomes a rather blurry line
(IMO) which generalizes which, and on the meanwhile I find it most nice
to use the abstraction that expresses the actual idea as directly as
possible.  And since breaking from a loop or returning from a block are
inherently escape-only actions, I think it's actually nicer to use
`let/ec' for those cases even in terms of code clarity etc.