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Re: short-circuiting logical operations on constexpr predicates

From: Thiago Macieira <thiago_at_[hidden]>
Date: Wed, 16 Nov 2022 11:17:22 -0800
On Wednesday, 16 November 2022 06:42:58 PST Jason McKesson via Std-Discussion
> The literal
> text of the source code makes no sense, as far as the language is
> concerned. It is no different than if you wrote `a + - + - + c`.

Note, this expression *does* make sense and is allowed. The first + is the
binary addition operator; all the rest are unary prefixes. So this expression

  a + (-(+(-(+c))))

If you remove the idempotent unary plus, you get

  a + (-(-c))

And two negations is the same as doing nothing (ignoring the UB at INT_MIN),
resulting in a simple addition

  a + c

Similarly, both a+++c and a---c are permitted, as are a*/*/*/c and a/*/*/*c.

None of those should pass a code review, of course.

Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel DCAI Cloud Engineering

Received on 2022-11-16 19:17:25