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Scala, Patterns and The Perl Effect

19 replies on 2 pages. Most recent reply: Sep 22, 2013 9:26 AM by Oliver Plohmann

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Flat View: This topic has 19 replies on 2 pages [ « | 1 2 ]
Trond Olsen

Posts: 14
Nickname: tolsen
Registered: Mar, 2007

Re: Scala, Patterns and The Perl Effect Posted: Dec 25, 2011 9:55 AM
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Further extending the example with a catch-all clause:

val f4: PartialFunction[Any,String] = {
case _ => "undefined"
}
// f4: PartialFunction[Any,String] = <function1>

val f5 = f3 orElse f4
// f5: PartialFunction[Any,String] = <function1>

f5("a")
// res3: String = undefined

Channing Walton

Posts: 32
Nickname: channing
Registered: May, 2003

Re: Scala, Patterns and The Perl Effect Posted: Dec 30, 2011 6:41 PM
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Here is a another simple, concrete example.

val root:PartialFunction[Int, Double] = {
case x if x >=0 => math.sqrt(x)
}

val printIt:PartialFunction[Int, String] = { case i => "Root(" + i + ")"}

val roots = root orElse printIt

(-3 to 3) map (roots(_))
= Vector(Root(-3), Root(-2), Root(-1), 0.0, 1.0, 1.4142135623730951, 1.7320508075688772)

philippos papadatos

Posts: 6
Nickname: firesoft
Registered: Mar, 2012

Re: Scala, Patterns and The Perl Effect Posted: Mar 28, 2012 10:02 PM
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I’m in the process of evaluating scala for a new project.
The Perl effect indeed! I had a look at scala's website and i downloaded the free ebook.
I don't know about you but for me it feels like common best practices in Scala introduce very cryptic syntax in order to produce one liners. I don't see the value in that , I rather keep my code base stupidly simple, rather to reduce LOC, which at a glance can make sense rather spend 1-2 minutes figuring out what each line do.
Where is the productivity of scala then is it all hype ?
I don't know about you but i almost never write a component once and move on, i almost always revisit the code and make improvements- modifications. I feel with scala if i revisit a part of my code base say after a few months it will take me a long time to figure out what i was doing then!
I mainly use java & python and i don't see the benefits of Scala. If i need functional - dynamic features i use python and the combination of java + jython is very appealing to me.

Any suggestions on what Scala brings to the table?

philippos papadatos

Posts: 6
Nickname: firesoft
Registered: Mar, 2012

Re: Scala, Patterns and The Perl Effect Posted: Nov 28, 2012 7:19 AM
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well upon further investigation Scala is very interesting and complex ! if choose to make it complex...

Oliver Plohmann

Posts: 13
Nickname: olli
Registered: Jun, 2008

Re: Scala, Patterns and The Perl Effect Posted: Sep 22, 2013 9:26 AM
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This is the code from the article:

List(41, "cat") collect { case i: Int ⇒ i + 1 }

The equivalent Smalltalk code looks like this:


| list |
list := OrderedCollection new add: 41; add: "cat"; yourself.
(list select: [ :each | each isInteger]) collect: [ :each | each + 1]

So the Scala solution is more concise as the concatenation of select and collect is shorter. Nevertheless, also in a dynamically typed languages like Smalltalk people don't throw strings and ints into the same collection. Especially in a dynamically typed language this will likely result in runtime errors that don't disappear until you made this collection only contain elements of a common type.

I really don't understand what message the author wants to convey. If I want to understand what partial functions are, then I will have a look into the book by Odersky and I hope the sample code is not simply a mess eben a Python/Ruby/Perl/Smalltalk/etc. developer wouldn't write. Okay, I was a bit rough. But the way Scala is explained sometimes misses a bit rigor.

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