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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.c
Subject: Re: Recursion, Yo
Date: Sun, 14 Apr 2024 22:47:26 +0100
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bart <bc@freeuk.com> writes:

> On 14/04/2024 11:17, Ben Bacarisse wrote:
>> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>> 
>>> On Sat, 13 Apr 2024 19:37:37 +0200, Janis Papanagnou wrote:
>> ...
>>>> But maybe you can explain where or how there's something "thrown away".
>>>
>>> This is a valid Algol 68 program (just tested with a68g):
>>>
>>>      BEGIN PROC f = REAL : 3.1415; f END
>>>
>>> It calls f, which returns a real, which is then cast to VOID -- i.e.
>>> thrown away.
>> You are just arguing about how you want to use an informal term: namely
>> to "throw away".  In Algol 68, the mode (AKA type) "void" is,
>> conceptually, a collection of values like any other.  The coercion
>> called voiding converts a value of some other type to the single value
>> of type void.  You could describe this a "throwing away the value", or
>> you could agree with Janis and say that the serial-clause you wrote
>> yields the sole value of type void.
>
> It looks to me as though it yields a type REAL, as would this:
>
>    BEGIN 1.23 END
>
> If the context has no need for such a type, then it is discarded (although
> my own language would report an error for constructs like this that make no
> sense by themselves; most likely it is an actual mistake).
>
> But in one like this:
>
>    REAL x := BEGIN 1.23 END
>
> Then that REAL value would be utilised.

But what post posted was a whole program.  The context -- it being the
top-level serial clause matters.  I think.  I say I think because I'd
like to find the wording that makes this so.  a68g says it, but a68g is
an implementation and not the final word.

-- 
Ben.