Mathematica：摆脱“x ->”在 FindInstance 结果中

发布于 2024-08-09 07:42:35 字数 444 浏览 1 评论 0原文

假设我有以下结果：

a=FindInstance[2*b^2 + b^3 == b^4 + t && t < 10 && t > -1, {b, t}, 
  Integers, 20]
{{b -> -1, t -> 0}, {b -> 0, t -> 0}, {b -> 1, t -> 2}, {b -> 2, 
  t -> 0}}

如何去掉“b->”然后就得到 b 答案的数组？我可以做到一半：

a[[All,1]]
{b -> -1, b -> 0, b -> 1, b -> 2}

但我怎样才能做到：

{-1, 0, 1, 2}

谢谢

原文

Suppose I have the following results:

a=FindInstance[2*b^2 + b^3 == b^4 + t && t < 10 && t > -1, {b, t}, 
  Integers, 20]
{{b -> -1, t -> 0}, {b -> 0, t -> 0}, {b -> 1, t -> 2}, {b -> 2, 
  t -> 0}}

How can I get rid of the "b->" and just get the array of b answers? I can get halfway there with:

a[[All,1]]
{b -> -1, b -> 0, b -> 1, b -> 2}

but how can I get to just:

{-1, 0, 1, 2}

Thanks

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

深海夜未眠 2024-08-16 07:42:36

我可能会从 dreeves 的答案中遗漏一些东西，但我一直相信你这样做的方式只是通过写作：

b /. a

Solve 函数的文档，它使用相同的输出样式。

I might be missing something from dreeves' answer, but the way I always believed you do this was simply by writing:

b /. a

There is an example of this in the "Basic Examples" section of the documentation for the Solve function, which uses the same output style.

回复收藏 0 原文

眼睛会笑 2024-08-16 07:42:36

尽管威尔的答案是规范的方法，但我将提供一些替代方案只是为了好玩。

In[37]:= ans={{b -> -1, t -> 0},{b -> 0, t -> 0},{b -> 1, t -> 2},{b -> 2, t -> 0}};

In[38]:= Cases[ans, (b -> a_) :> a, Infinity]

Out[38]= {-1, 0, 1, 2}

In[39]:= ans[[All, 1]][[All, 2]]

Out[39]= {-1, 0, 1, 2}

In[40]:= ans /. {b -> a_, _} :> a

Out[40]= {-1, 0, 1, 2}

In[41]:= (ans /. Rule -> List)[[All, 1, 2]]

Out[41]= {-1, 0, 1, 2}

Though Will's answer is the canonical way to do it, I'll provide a few alternatives just for fun.

In[37]:= ans={{b -> -1, t -> 0},{b -> 0, t -> 0},{b -> 1, t -> 2},{b -> 2, t -> 0}};

In[38]:= Cases[ans, (b -> a_) :> a, Infinity]

Out[38]= {-1, 0, 1, 2}

In[39]:= ans[[All, 1]][[All, 2]]

Out[39]= {-1, 0, 1, 2}

In[40]:= ans /. {b -> a_, _} :> a

Out[40]= {-1, 0, 1, 2}

In[41]:= (ans /. Rule -> List)[[All, 1, 2]]

Out[41]= {-1, 0, 1, 2}

回复收藏 0 原文

~没有更多了~