Re: Unsafe code blocks

From	Michael S <already5chosen@yahoo.com>
Newsgroups	comp.os.vms
Subject	Re: Unsafe code blocks
Date	2025-11-19 19:29 +0200
Organization	A noiseless patient Spider
Message-ID	<20251119192953.00005981@yahoo.com> (permalink)
References	<10f4oi1$25lkk$2@dont-email.me> <10fbc6h$4hb$1@reader2.panix.com> <10fig0p$1n41a$2@dont-email.me> <10fig54$1n41a$3@dont-email.me> <10fkq9g$8f$1@reader2.panix.com>

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On Wed, 19 Nov 2025 16:12:32 -0000 (UTC)
cross@spitfire.i.gajendra.net (Dan Cross) wrote:

> In article <10fig54$1n41a$3@dont-email.me>,
> Arne Vajh_¸j  <arne@vajhoej.dk> wrote:
> >On 11/18/2025 2:04 PM, Arne Vajh_¸j wrote:  
> >> On 11/15/2025 9:16 PM, Dan Cross wrote:  
> >>>> Also note the availability of the 'Valid attribute to make sure
> >>>> that what
> >>>> is in the variable after the unsafe conversion is actually a
> >>>> valid value.  
> >>>
> >>> Sum types make this trivial:
> >>>
> >>> _ _ _ _  impl SomeType {
> >>> _ _ _ _ _ _ _ _  fn try_from(i: i32) -> Option<Self> {
> >>> _ _ _ _ _ _ _ _ _ _ _ _  // if valid, return `Some(whatever`),
> >>> _ _ _ _ _ _ _ _ _ _ _ _  // else return `None`.
> >>> _ _ _ _ _ _ _ _  }
> >>> _ _ _ _  }  
> >> (assuming Option in Rust is what it is in other languages)
> >> 
> >> Option and Ada Valid are somewhat different.
> >> 
> >> Option is a way for a function/method to either return
> >> a value or return the fact that there is no value.
> >> 
> >> A much better way to do that than traditional
> >> return null or -1 or whatever to indicate there
> >> is no value.
> >> 
> >> Ada valid attribute is a runtime check on the result from
> >> an unsafe conversion to see if it meets the constraints
> >> of the data type.  
> >
> >Option is in fashion in recent years.  
> 
> Algebraic data types have been used in functional languages
> since the 1970s, starting with the "Hope" language from
> Edinburgh.  ML took them from Hope and popularized them, and
> they leaked into Miranda, Haskell, and OCaml from there.  Now
> many languages support them; even C++ (`std::optional`).
> 
> Hope was first described in a paper in 1980, but the work of
> course predated that.
> 
> That makes them about as old as VMS, and older than Ada.  In
> other words, they've been "In Fashion" since the 70s,

That does not follow.
Something existing for a long time is not the same as being fashionable
for a long time.
Options became fashionable relatively recently, as result of growing
dissatisfaction with previous fashionable item - exceptions.
Parts of programming community that are less concerned with fashion of
the day ignored both of this things. They use error codes, either in
crude form (like C) or more refined (like Go).

> which as
> far as all things fashion goes, is a pretty good run;
> particularly considering some of the things that were popular in
> that decade.
> 
> >There are not that many languages on VMS supporting
> >Option.
> >
> >Scala does - Option[T].
> >
> >And Java 8 Optional<T> is almost the same.  
> 
> More's the pity.
> 
> 	- Dan C.
>

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Unsafe code blocks Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2025-11-13 14:04 +0000
  Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-13 15:44 -0500
  Re: Unsafe code blocks Marc Van Dyck <marc.gr.vandyck@invalid.skynet.be> - 2025-11-14 12:14 +0100
    Re: Unsafe code blocks John Reagan <johnrreagan@earthlink.net> - 2025-11-14 11:47 -0500
      Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-14 14:02 -0500
        Re: Unsafe code blocks Marc Van Dyck <marc.gr.vandyck@invalid.skynet.be> - 2025-11-17 09:25 +0100
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-17 14:58 -0500
            Re: Unsafe code blocks Chris Townley <news@cct-net.co.uk> - 2025-11-17 20:11 +0000
              Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-17 15:47 -0500
            Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-18 13:10 +0000
      Re: Unsafe code blocks Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-11-14 19:32 +0000
    Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-14 13:55 -0500
      Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-14 20:00 -0500
        Re: Unsafe code blocks Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2025-11-17 18:56 +0000
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-17 14:22 -0500
  Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-16 02:16 +0000
    Re: Unsafe code blocks Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2025-11-17 19:22 +0000
      Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-17 14:55 -0500
        Re: Unsafe code blocks Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> - 2025-11-17 20:33 +0000
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-17 15:55 -0500
      Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-18 12:54 +0000
    Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-18 14:04 -0500
      Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-18 14:07 -0500
        Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-19 16:12 +0000
          Re: Unsafe code blocks Michael S <already5chosen@yahoo.com> - 2025-11-19 19:29 +0200
            Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-19 19:00 +0000
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-19 12:41 -0500
            Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-19 18:19 +0000
              Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-19 14:21 -0500
                Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-19 19:49 +0000
      Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-19 16:02 +0000
        Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-19 20:26 -0500
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-19 20:31 -0500
          Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-19 21:32 -0500
          Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-20 11:54 +0000
            Re: Unsafe code blocks Arne Vajhøj <arne@vajhoej.dk> - 2025-11-20 19:18 -0500
              Re: Unsafe code blocks cross@spitfire.i.gajendra.net (Dan Cross) - 2025-11-21 03:03 +0000

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