29 Numerics library [numerics]

29.9 Basic linear algebra algorithms [linalg]

29.9.7 Exposition-only helpers [linalg.helpers]

29.9.7.1 abs-if-needed [linalg.helpers.abs]

1
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The name abs-if-needed denotes an exposition-only function object.
The expression abs-if-needed(E) for a subexpression E whose type is T is expression-equivalent to:
  • (1.1)
    E if T is an unsigned integer;
  • (1.2)
    otherwise, std​::​abs(E) if T is an arithmetic type,
  • (1.3)
    otherwise, abs(E), if that expression is valid, with overload resolution performed in a context that includes the declaration template<class T> T abs(T) = delete;
    If the function selected by overload resolution does not return the absolute value of its input, the program is ill-formed, no diagnostic required.