Subject: Re: [std-proposals] proposal: new const-able feature ( use "const?" , or new "constable" keyword) for method/function
From: Bo Persson (bo_at_[hidden])
Date: 2019-12-18 03:25:10
On 2019-12-17 at 22:20, jianping z via Std-Proposals wrote:
> Thank you and Michael Hava for the updates, it turns out my C++
> knowledge needs to be updated to C++17.
> Here are some of my thoughts about your concern,
> 1. the "&&?" notation
> we may treat "&&" as a token having two "&", and each "?" can optionally
> remove one "&",
> following the rule, "&&??" can be used to optionally remove two "&" from
> "&&" with "??".
> a) const?Â Â Â -> (), constÂ Â //2 variations with single "?"
> b) &?Â Â Â Â Â Â Â -> (), &Â Â Â Â Â Â //2 variations with single "?"
> c) &&?Â Â Â Â Â Â -> &, &&Â Â Â Â Â Â //2 variations with single "?"
> d) &&??Â Â Â Â Â -> (), &, &&Â Â //3 variations with double "?" ("??")
> here, left side is the notations, right side are the variations of the
> final tokens to replace the notation, "()" means no token (notation removed)
> by explaining "?" like this, developer may able to accept this concept
> easily. though "&?", and "&&??" are hardly needed, but they may still be
> usefully, for example
Readability concerns aside, using double question marks gets you very
close to accidentally stumble into trigraphs. Although now formally
removed from C++, several compilers still support them as an extension.
For example, see "What does the C ??!??! operator do?"
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