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Re: ttn-pers-scheme 0.19 available

From: Marius Vollmer
Subject: Re: ttn-pers-scheme 0.19 available
Date: 19 May 2001 13:37:09 +0200
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.0.102

thi <address@hidden> writes:

>       - (ice-9 rdelim) required for `read-line' and friends, but
>         `use-modules' no longer can be conditionalized, so the old
>         `(or (defined? 'read-line) (use-modules (ice-9 rdelim)))'
>         workaround no longer works.

`use-modules' *can* be conditionalized.  The trick is to observe that
use-modules can only be used at top-level, but that the arms of an
`if' or the clauses in a `cond' are still on top-level when the
outermost form is.  The arguments of a `or' are on top-level in Guile,
but you shouldn't count on this.

So, this oughta work

    (if (not (defined? 'read-line))
        (use-modules (ice-9 rdelim)))

Of course, you would give the hypothetical compiler a hard time with

It is probably better to move conditional module system operations to
macro-expansion time.  Could `cond-expand' be extended to allow for
more general tests?

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