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回复 1# centos_71
A strict weak ordering is a binary relation < on a set S that is a strict partial order (a transitive relation that is irreflexive, or equivalently,[5] that is asymmetric) in which the relation "neither a < b nor b < a" is transitive.
也就是说“strict weak ordering”满足以下几个条件
1、对于给定集合S,其中任意两个元素a和b都存在ordering,这一点和“partial ordering”不同,后者不能保证任意两个元素之间都存在ordering,所以才叫“partial”
2、transitive指如果a<b且b<c,则a<c
3、irreflexive是指a<a一定为假
4、asymmetric指若a<b,则b<a为假
5、最后一句说的是“(not a<b) and (not b<a)”有传递性,也就是说,如果“(not a<b) and (not b<a)”且“(not b<c) and (not c<b)”,则“(not a<c) and (not c<a)”
STL里的less定义就需要满足以上条件 |
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