Idiom for alerting user who attempts to use a non-enabled Rust feature

[dcnorris]

This comment by @adri326 dcnorris@157c35c#r151199171 points to a need (perhaps) for a uniform approach to alerting users when they attempt to load a library requiring a Rust feature that has not been enabled.

Does Scryer (or the ISO Standard) already establish an approach for this?

[dcnorris]

Closing as irrelevant; see #2765 (comment).

[triska]

It still seems interesting even if it may not be needed for this concrete functionality! Other predicates are already affected.

[hurufu]

Some Prolog implementations (YAP, SWI) allow configuration of Prolog execution environment using set_prolog_flag/2, current_prolog_flag/2 and (non-portable) create_prolog_flag/3. It might be used to check whether special math functions are supported.