Scheme - About continuation

Author

About continuation

CrazyCorn

2005-08-16, 4:01 am

Hi,I'm new here.
I find a problem when I try to understand continuation with R5RS.
I can't understand why the code below gives the answer -1:

(call-with-values * -)

Could you help me?Thanks a lot.

Anton van Straaten

2005-08-16, 4:01 am

CrazyCorn wrote:
> Hi,I'm new here.
> I find a problem when I try to understand continuation with R5RS.
> I can't understand why the code below gives the answer -1:
>
> (call-with-values * -)
>
> Could you help me?Thanks a lot.

This doesn't really have much to do with continuations specifically.

R5RS defines that (*) returns 1, which is for mathematical reasons.
Call-with-values treats its first argument as a "producer" procedure,
and calls it without arguments. This means that (call-with-values * -)
will first evaluate (*) and obtain the defined answer of 1. It then
applies its "consumer" procedure to this argument, which in this case
means evaluating (- 1). This results in -1.

Anton

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