Post on 14-Sep-2014
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λ the eχtremetest-driving a functional language
07/30/2014
PREPARED BYTim MyerProgrammertmyer@solutionsiq.com
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λ the eχtreme: test-driving a functional language
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“
”
λ the eχtreme: test-driving a functional language
Scala: you stare at your foot for 3 days without any sleep, you then figrue [sic] out how to shoot yourself in the foot with one line of code… recursively.
Comment from Roberto Leibman on How to Shoot Yourself in the Foot in Any Programming Language
by Mike Walker
4λ the eχtreme: test-driving a functional language
AgendaΛ Tools of the TradeΛ First testΛ A synchronicityΛ Network independenceΛ More of the sameΛ Changing StationΛ And so on and so forth and so on….
5λ the eχtreme: test-driving a functional language
Prelude
6
The Little Schemer
λ the eχtreme: test-driving a functional language
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“
”λ the eχtreme: test-driving a functional language
if you look at the features Scala provides, it is substantially a
functional language, but on the surface it does not always look
like one, and it does not force you to adopt the functional style.
For many of its users, the functional programming constructs in
Scala are the most important set of tools it has to offer but they
are not the only tools. In fact, great care has been spent in the
Scala design to make functional constructs, imperative
constructs, and objects all play well together. I think
postfunctional is a good term for that blend.
- Martin OderskyA Postfunctional Language
8λ the eχtreme: test-driving a functional language
Tools
Λ Git
Λ Maven
Λ Scala IDE
Λ A Dropbox account
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TheBeginning
Where do we start?
We can start atTheBeginning.
λ the eχtreme: test-driving a functional language
How can we dothat?
Check it out!
10λ the eχtreme: test-driving a functional language
$ git clone https://github.com/timezra/LambdaTheExtreme.git && cd LambdaTheExtreme $ git checkout tags/TheBeginning
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TheBeginning
We got git, now do we get an elephant?
We get a canary instead.
λ the eχtreme: test-driving a functional language
12λ the eχtreme: test-driving a functional language
Canary
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Canary
What does a canaryhave to do with this?
It’s an earlyindication thatsomething has gone very wrong.
λ the eχtreme: test-driving a functional language
14λ the eχtreme: test-driving a functional language
$ git checkout tags/Canary
15λ the eχtreme: test-driving a functional language
Interlude
16λ the eχtreme: test-driving a functional language
Recap
Λ A Case Class
Λ An Object
Λ A FeatureSpec
Λ A FunSpec!
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Canary
Can our canary getaccount info?
Only with aDropbox account.
λ the eχtreme: test-driving a functional language
18λ the eχtreme: test-driving a functional language
Actors
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Actors
What happenswhen our accountinfo changes?
Our expectation is wrong.
λ the eχtreme: test-driving a functional language
What happenswhen we changeour expectation?
Our test fails.
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Actors
Why does it fail?
Ourimplementation is wrong.
λ the eχtreme: test-driving a functional language
Where do we findthe rightimplementation?
Look in the upperleft.
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$ git checkout tags/Actors
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Actors
How can we callDropbox?
Using HTTP
λ the eχtreme: test-driving a functional language
How will Dropbox know us?
We’ll give it atoken.
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Actors
When will we getour account info?
In the future!
λ the eχtreme: test-driving a functional language
24λ the eχtreme: test-driving a functional language
Interlude
25λ the eχtreme: test-driving a functional language
Recap
Λ Configuration Management
Λ Implicit conversions
Λ An Actor
Λ An Actor Testkit
Λ The Future!
26λ the eχtreme: test-driving a functional language
Care and Feeding
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MinedReading
What happens if wefail?
You tell me!
λ the eχtreme: test-driving a functional language
Do we catch anexception?
We intercept it.
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MinedReading
Sprechen SieDeutsch?
Wenn Sie möchten
λ the eχtreme: test-driving a functional language
29λ the eχtreme: test-driving a functional language
$ git checkout tags/MinedReading
30λ the eχtreme: test-driving a functional language
Etude
31λ the eχtreme: test-driving a functional language
Recap
Λ Stubbing a probe’s return value
Λ Intercepting an expected exception
Λ Iterating over an optional value
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Putting it out there
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Zed
May I sharesomething withyou?
Of course!
λ the eχtreme: test-driving a functional language
I would rather youput than post.
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Zed
What if I don’t havea file lying around?
You can shareanything you likeover the web.
λ the eχtreme: test-driving a functional language
But how will youknow what itshould look like onthe other side?
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Zed
Who’s Zed?
Maybe Zed canhelp.
λ the eχtreme: test-driving a functional language
Scalaz!
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$ git checkout tags/Zed
37λ the eχtreme: test-driving a functional language
Interlude
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Zed
Of course!
Does Zed useMonads?
λ the eχtreme: test-driving a functional language
Where’s a gooddefinition of whata Monad is? Anywhere but
urbandictionary.com
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Zed
This one is pretty good:You Could Have Invented Monads!
λ the eχtreme: test-driving a functional language
The original is still the best:Monads for functional programming
For today, we can look at them as a wayof chaining operations.
40λ the eχtreme: test-driving a functional language
Recap
Λ Implicit transformation from a File to an abstract representation of its contents
41λ the eχtreme: test-driving a functional language
Birds of a feather
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Bof
We just need a littlecoordination.
What if I want toshare all mypictures ofcanaries withfriends at once?
λ the eχtreme: test-driving a functional language
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Bof
Recursivetraversal fits a treelike a glove.
How about a littlerecursion?
λ the eχtreme: test-driving a functional language
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$ git checkout tags/Bof
45λ the eχtreme: test-driving a functional language
Interlude
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CallCC
And on and on?
But what happensif the recursiongoes on and on?
λ the eχtreme: test-driving a functional language
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CallCC
And on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on and on
λ the eχtreme: test-driving a functional language
48λ the eχtreme: test-driving a functional language
Recap
Λ Changing recursive traversal to iterative using continuations
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To be continued….
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