I would argue against complexity and pro singular responsibility.
Streams should only be used streaming (read/write)
regex should only be used for parsing/pattern matching.
Keep them separate.

In the first place, I am not a fan of regex but your example implementation
only parsed a single argument. regex's utility comes from complex
multi-argument parsing. Are you going to make an operator>>() that takes a
runtime regular expression and an out param returning a collection of
matches.

Or might you set a regex stream mode where the next N args would be the
matching expressions and how would you get the count of matches before
trying to read the matches.

in >> regex(".....") >> arg1 >> arg2>> ... >> argN; //NOT
recommending anything like this.

Ridiculous suggestion to show the lunacy of mixing streaming with parsing:
If you are going to do a regex streaming, why not a streaming scanf() type
streaming parsing mode. That would almost make more sense since
most operator>>() have a symmetrical operator<<() functionality (vis-à-vis
streaming formatted print(...) ).


On Thu, Feb 20, 2025 at 5:48 AM Phil Bouchard via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> Greetings,
>
> Seems to me regex over istreams would be quite useful. Here's an
> inefficient implementation:
>
>
> inline std::istream& operator >> (std::istream& in, std::string & v)
> {
> static const std::regex string_regex(R"(^\"(.*?)\"$)");
>
> std::smatch match;
>
> std::string x;
>
> for (x += in.get(); in; x += in.get())
> if (std::regex_match(x, match, string_regex))
> {
> v = match[1].str();
>
> return in;
> }
>
> throw std::invalid_argument("Parse error.");
> }
>
> Is there any interests in such implementation?
>
>
> Regards,
> --
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> Founder & CEO
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