It is not even required that a + b == a + b
. One of the subexpressions may hold the result of the addition with more precision than the other one, for example when the use of multiple additions requires one of the subexpressions to be temporarily stored in memory, when the other subexpression can be kept in a register (with higher precision).
If a + b == a + b
is not guaranteed, a + b == b + a
cannot be guaranteed. If a + b
does not have to return the same value each time, and the values are different, one of them necessarily will not be equal to one particular evaluation of b + a
.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…