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Subject: [std-proposals] std::nabs (negative abs) idea
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2021-02-12 10:37:15


Hi,

I've been contemplating a possible new standard function std::nabs,
which would return a negated absolute value of its argument:

   assert(std::nabs(1) == -1);

   assert(std::nabs(-1) == -1);
   assert(std::nabs(0) == 0);

The idea behind this addition is that, unlike std::abs, this function
will never cause a signed integer overflow. This is because in two's
complement representation, which is mandatory since C++20, any positive
integer can be negated without overflow, but not vise versa.

I wonder if this idea has come up before.


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