Re: Permutation Generator

john@xxxxxxxxxxxxxx wrote:

> Hermann's version gives error "force: expects argument of type
> <promise>; given ()" in DrScheme, but perhaps he has deliberately left
> some little error in it or is using another version of force. But as I
> said, it's not for a homework assignment (I'm not studying CS anyway),
> and the lazy stream version by John Gilson works like a charm. Thanks a
> lot!!!

The semantic of Gambit-C force is
(lambda (x) (if (promise? x) (force x) x)).
This should explain the error message.

Regards
Hermann
.

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