Freewind

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visits member for 8 months
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A programmer from China, I love:

  1. Java, Scala, Groovy, Xtend
  2. Playframework

Welcome joining my QQ group:

  1. Scala热情交流群 ( 132569382 )
  2. Play热情交流群 ( 168013302 )
  3. JavaScript热情交流群 ( 168013483 )

27 Actions

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Apr
10
 awarded  Favorite Question
Mar
7
 revised Is `1+101=110` a proposition?
added 200 characters in body
Mar
7
 comment Is `1+101=110` a proposition?
I just translated some content of that book to English. See my updated question.
Mar
7
 revised Is `1+101=110` a proposition?
added 602 characters in body
Mar
7
 comment Is `1+101=110` a proposition?
It's an old Chinese book, that you can't find English verions.
Mar
7
 asked Is `1+101=110` a proposition?
Jan
7
 accepted Is it reflexive: everyone who has visited Web page a has also visited Web page b, for all webpages
Jan
7
 awarded  Editor
Jan
7
 revised Is it reflexive: everyone who has visited Web page a has also visited Web page b, for all webpages
added 486 characters in body
Jan
7
 comment Is it reflexive: everyone who has visited Web page a has also visited Web page b, for all webpages
If page $x$ has never been visited, that $F(p,x)$ will always be false, that $\forall p (F(p,x) \to F(p,y))$ will be true, so $(x, any y)$ belong to $R$.
Jan
7
 comment Is it reflexive: everyone who has visited Web page a has also visited Web page b, for all webpages
$R$={$(x,y) | \forall p (F(p,x) \to F(p,y))$}, where $F(p,x)$ means "p has visited x". Is it right?
Jan
7
 asked Is it reflexive: everyone who has visited Web page a has also visited Web page b, for all webpages
Jan
7
 awarded  Supporter
Jan
7
 accepted Relation $R$ is $xy\ge1$, and $x\in \mathbb{Z}$ and $y\in\mathbb{Z}$, is $R$ reflexive?
Jan
6
 comment Relation $R$ is $xy\ge1$, and $x\in \mathbb{Z}$ and $y\in\mathbb{Z}$, is $R$ reflexive?
@OldJohn,could you please make you comment an answer, and I will accept it? Thanks.
Jan
6
 comment Relation $R$ is $xy\ge1$, and $x\in \mathbb{Z}$ and $y\in\mathbb{Z}$, is $R$ reflexive?
I understand now! I misunderstood the definition of reflexive: A relation R on a set A is called reflexive if (a, a) ∈ R for every element a ∈ A.. There is every element a ∈ R, so we must consider 0.
Jan
6
 comment Relation $R$ is $xy\ge1$, and $x\in \mathbb{Z}$ and $y\in\mathbb{Z}$, is $R$ reflexive?
If x or y is zero, that xy≥1 will be false, so (x,y)∉R.
Jan
6
 asked Relation $R$ is $xy\ge1$, and $x\in \mathbb{Z}$ and $y\in\mathbb{Z}$, is $R$ reflexive?
Nov
19
 awarded  Notable Question
Sep
4
 awarded  Scholar
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