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Corrected documentation for 'table.sort'

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The sort function must define a (strict) weak order for a correct
sorting. A partial order is not enough.
This commit is contained in:
Roberto Ierusalimschy 2021-01-14 13:26:55 -03:00
parent b07fc10e91
commit 825ac8eca8
1 changed files with 8 additions and 8 deletions
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@ -7821,19 +7821,19 @@ from @T{list[1]} to @T{list[#list]}.
If @id{comp} is given,
then it must be a function that receives two list elements
and returns true when the first element must come
before the second in the final order
(so that, after the sort,
@T{i < j} implies @T{not comp(list[j],list[i])}).
before the second in the final order,
so that, after the sort,
@T{i <= j} implies @T{not comp(list[j],list[i])}.
If @id{comp} is not given,
then the standard Lua operator @T{<} is used instead.
Note that the @id{comp} function must define
a strict partial order over the elements in the list;
that is, it must be asymmetric and transitive.
Otherwise, no valid sort may be possible.
The @id{comp} function must define a consistent order;
more formally, the function must define a strict weak order.
(A weak order is similar to a total order,
but it can equate different elements for comparison purposes.)
The sort algorithm is not stable:
elements considered equal by the given order
Different elements considered equal by the given order
may have their relative positions changed by the sort.
}