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Now it’s time to work that gray matter! Do the following exercises to be sure you have grasped the concepts that were presented in this chapter. Don’t skip this!

1. What is the definition of a closure?

2. Identify the free variable in the following:

 ​ ​def​ is_larger_than(amount) ​ lambda ​do​ |a| ​ a > amount ​ ​end​ ​ ​end​

Here’s an example run:

 ​ ​>>​ larger_than_5 = is_larger_than(5) ​ ​ ​>>​ larger_than_5.call(4) ​ ​=>​ ​false​ ​ ​ ​>>​ larger_than_5.call(5) ​ ​=>​ ​false​ ​ ​ ​>>​ larger_than_5.call(6) ​ ​=>​ ​true​
3. You work in a music store and you’ve been tasked with writing a miniature database to store artists and album titles. The database should be able to insert, delete, and list entries, but you cannot use objects ...

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