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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: Example usage of new flag use_strict [DOG] (Was: Is there room to
 adopt a flag strict_iso?)
Date: Tue, 24 Jun 2025 18:06:13 +0200
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In-Reply-To: <103ei2s$18c05$1@solani.org>


So it would only change the conformity of those built-ins,
flags etc.. mentioned in the ISO core standard. But
otherwise it would be open to extensions. Its a
missing row in @jschimpf table:

Mode	Description	Origin
eclipse_language	ISO heavily violating and implementation specific	ECL
iso	ISO conforming and implementation specific	ECL
iso_strict	ISO conforming and no implementation specific	ECL
~use_strict	ISO sloppy conforming, combineable with iso / iso_strict	DOG

Here is a hypothetical scenario in ECLiPSe Prolog
if it had this flag:

[eclipse 1]: X is floor(1).
type error: expected float, found 1 in floor(1, X)
Abort

[eclipse 2]: set_prolog_flag(use_strict, off).
Yes (0.00s cpu)

[eclipse 1]: X is floor(1).
X = 1
Yes (0.00s cpu)

In JavaScript type=“module” the system starts with
use_strict opted in. Only JavaScript without type=“module”,
for example the extension .js and not the extension .mjs,
start with use_strict off, and can opt in.

Typically a JavaScript top-level such as the
Chrome console, starts with use_strict off.

Mild Shock schrieb:
>  > **iso_strict** is ISO-conforming strict mode, providing
>  > only ISO features and no implementation specific ones
> 
> Maybe a good name would then be "use_strict", instead
> of "strict_iso", if a permutation of it is already
> used in the form "iso_strict" by ECLiPSe Prolog.
> "use_strict" would be motivated from JavaScript:
> 
>  > JavaScript's strict mode is a way to *opt in* to a
> restricted variant of JavaScript, thereby implicitly
> opting-out of "sloppy mode". Strict mode isn't just a subset:
> it *intentionally* has different semantics from normal
> code. Strict mode code and non-strict mode code can
> coexist, so scripts can opt into strict mode incrementally.
> 
> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode 
> 
> 
> In JavaScript the mode is local. You can place the
> "use_strict" directive inside any function you want, and
> opt in to this function and all sub functions.
> So "use_strict=on" would mean ISO conforming.
> 
> This would solve the problem that some Prolog systems
> have an "iso" flag, but setting it to true does not
> imply they become 100% ISO conforming. It rather tells
> the system to have the behaviour of some
> 
> predicates change to ISO conforming. So the "use_strict"
> would be a conformity flag, and not a scope flag. It
> would not reduce the scope of a Prolog system or a
> Prolog modul to use less built-ins, flags etc..