Add Use A Case Statement As A Cond Statment as a ruby til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
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+_493 TILs and counting..._
 
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@@ -385,6 +385,7 @@ _492 TILs and counting..._
 - [Uncaught Exceptions In Pry](ruby/uncaught-exceptions-in-pry.md)
 - [`undef_method` And The Inheritance Hierarchy](ruby/undef-method-and-the-inheritance-hierarchy.md)
 - [Up And Down With Integers](ruby/up-and-down-with-integers.md)
+- [Use A Case Statement As A Cond Statement](ruby/use-a-case-statement-as-a-cond-statement.md)
 - [Who Are My Ancestors?](ruby/who-are-my-ancestors.md)
 - [Zero Padding](ruby/zero-padding.md)
 

ruby/use-a-case-statement-as-a-cond-statement.md

@@ -0,0 +1,29 @@
+# Use A Case Statement As A Cond Statement
+
+Many languages come with a feature that usually takes the name _cond
+statement_. It is essentially another way of writing an _if-elsif-else_
+statement. The first conditional in the _cond statement_ to evaluate to try
+will then have its block evaluated.
+
+Ruby doesn't have a _cond statement_, but it does have a _case statement_.
+By using a _case statement_ with no arguments, we get a _cond statement_. If
+we exclude arguments and then put arbitrary conditional statements after the
+`when` keywords, we get a construct that acts like a _cond statement_. Check
+out the following example:
+
+```ruby
+some_string = "What"
+
+case
+when some_string.downcase == some_string
+  puts "The string is all lowercase."
+when some_string.upcase == some_string
+  puts "The string is all uppercase."
+else
+  puts "The string is mixed case."
+end
+
+#=> The string is mixed case.
+```
+
+[source](http://www.skorks.com/2009/08/how-a-ruby-case-statement-works-and-what-you-can-do-with-it/)