I’ve compiled a guide on generating options tags using options_for_select.
Environment
- Ruby 2.2.3
- Rails 4.2.5
All posts by Kenji
(日本語) Rails: クラス名が ActiveRecord::AttributeMethods 内のモジュールと同じ場合
CoffeeScript: How to write For Loop
How to write for loop in CoffeeScript.
for loop of array
In Ruby, it is written as items.each.
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arr = ['a', 'b', 'c'] for item in arr alert item |
for loop of array with index
In Ruby, it is written as items.each_with_index.
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arr = ['a', 'b', 'c'] for item, index in arr alert index alert item |
Proof: Irrational numbers \( a \) , \( b \) exist that make \( a^b \) rational number
Irrational numbers ( a ) , ( b ) exist that make ( a^b ) rational.
Prove with law of excluded middle and without fixing what ( a ) and ( b ) are.
Proof
Supporse ( x = sqrt{2} ^ sqrt{2} ) .
Case: ( x ) is Rational
( sqrt{2} ) is irrational, so ( a = b = sqrt{2} ) make ( a^b ) rational. ( ( sqrt{2} ) が無理数であることの証明は 証明: ( sqrt{2} ) は無理数 をご覧ください。)
Case: ( x ) is Irrational
begin{eqnarray*} sqrt{2} & = & (sqrt{2}^sqrt{2})^sqrt{2} & = & sqrt{2}^{sqrt{2} cdot sqrt{2}} & = & sqrt{2}^2 & = & 2 end{eqnarray*}Then, ( a = x = sqrt{2}^sqrt{2} ) and ( b = sqrt{2} ) are irrational and make ( a^b ) rational.
Above all, there are irrational numbers ( a ) and ( b ) that make ( a^b ) rational.
OpenShift: What rhc setup does?
We can use the command rhc setup with OpenShift server. I tried it, and wrote what the command do.