Show HN: Clojure by Example

Re:Show HN: Clojure by Example by nerd_stuff on Wednesday June 10, 2015 @07:11PM (#9696291)

This is a great project!

I believe there's a lack of clarity in the let form explanation:

  =>(let [object "light"]
  =>  (let [object "darkness"])
  =>  (println (str "God said let there be " object)))
  God said let there be light
  nil

'object' is overwritten but only within the second let form:

  =>(let [object "light"]
  =>  (let [object "darkness"]
  =>    (println (str "God said let there be " object))))
  God said let there be darkness
  nil

or even:

  =>(let [object "light"]
  =>  (println (str "God said let there be " object))
  =>  (let [object "darkness"]
  =>    (println (str "God said let there be " object))))
  God said let there be light
  God said let there be darkness
  nil

The reason for this is the let form uses lexical scoping. In other words it creates a new frame which includes the bindings declared in the square brackets. When 'object' is evaluated its binding is looked for in the current frame, then the frame that called that frame and all the way out into the global namespace stopping when a binding is found.

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Re:Show HN: Clojure by Example by fnordsensei on Thursday June 11, 2015 @05:13AM (#9698552)

This would be better for illustrating that object is not overweritten, I think:

  =>(let [object "light"]
  =>  (let [object "darkness"]
  =>    (println (str "God said let there be " object)))
  =>  (println (str "God said let there be " object)))
  God said let there be darkness
  God said let there be light
  nil

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Re:Show HN: Clojure by Example by kimh on Saturday June 13, 2015 @04:19AM (#9710324)

Thanks for this. I added your example with slightly different form!

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Re:Show HN: Clojure by Example by kimh on Thursday June 11, 2015 @09:27AM (#9699549)

Thanks for your feedback! I think I could make it better.

http://kimh.github.io/clojure-by-example/#scope

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Re:Show HN: Clojure by Example by nerd_stuff on Thursday June 11, 2015 @11:06AM (#9700140)

Thank you!

I agree with fnordsensei's comment about ordering. You might also think about including this example from the docs which demonstrates bindings are immediately available:

    (let [x 1
          y x]
      y)
    -> 1

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