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add answers to exercise 1-5 chapter 7 #30

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Merged
merged 4 commits into from
Mar 27, 2016
Merged

add answers to exercise 1-5 chapter 7 #30

merged 4 commits into from
Mar 27, 2016

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ryblovAV
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Hi @axel22,
Pls see this answers

axel22
axel22 reviewed Mar 25, 2016
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src/main/scala/org/learningconcurrency/exercises/ch7/ex1.scala
def second_=(x: Q)(implicit txn: InTxn) = rSecond.single.transform(old => x)

def swap()(implicit e: P =:= Q, txn: InTxn): Unit = {
val old = Ref[P](first)
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It shouldn't be necessary to create a Ref object just to hold the value of the first field.
It is sufficient to read it via apply (i.e. just call first) and store the value of type P directly to the local variable.

val old = first

@axel22
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axel22 commented Mar 25, 2016

Thanks, looking good overall!

I only left some minor comments for exercise 1.

@ryblovAV
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@axel22
Thanks for your review, I'll try to fix

@ryblovAV
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Hi @axel22,
Pls, see my changes

I use asInstanceOf[P] method to convert Q => P.
Pls suggest me, does a better way exist ?

@axel22
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axel22 commented Mar 27, 2016

Unfortunately, not that I know of. Ideally, =:= class should have a reverse method that swaps the type parameters. Alternatively, you could require implicit =:= in both directions, but I guess this is good as it is!

LGTM

@axel22 axel22 merged commit 407a5cd into concurrent-programming-in-scala:master Mar 27, 2016
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axel22 commented Mar 27, 2016

Thanks for your contribution!

@ryblovAV
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Thanks for the review

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@ryblovAV @axel22