Is there a easy way to add tuples which contain addable elements like Int, Doubles etc? For examples,
(1,2) + (1,3) = (2,5)
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what are you trying to achieve? mostly using tuples for such thing (might be) considered bad style.Stefan Kunze– Stefan Kunze2013-10-26 14:03:57 +00:00Commented Oct 26, 2013 at 14:03
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tuples aren't intended for this type of thing. They're just a convenient wrapper for methods that return multiple values, which is why they don't have a host of useful functions like collections do.Luigi Plinge– Luigi Plinge2013-10-26 14:31:35 +00:00Commented Oct 26, 2013 at 14:31
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1I was trying to reduce a list of tuples. I am using tuples to do some map reduce type operations. Customs classes and objects seems overkill.Arun– Arun2013-10-26 15:24:58 +00:00Commented Oct 26, 2013 at 15:24
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@Arun, if you are working with lists of tuples you might find (my) project github.com/marklister/product-collections useful.Mark Lister– Mark Lister2013-10-27 09:11:33 +00:00Commented Oct 27, 2013 at 9:11
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3 Answers
import scalaz._, Scalaz._
scala> (1, 2.5) |+| (3, 4.4)
res0: (Int, Double) = (4,6.9)
There is an operator |+| for any class A with implicit Semigroup[A] in scope. For Int |+| is + by default (you could redefine it in your code).
There is an implicit Semigroup[(A, B)] for all tuples if there is implicit Semigroup for A and B.
See Scalaz cheat sheet.
Comments
+1 for the the Scalaz answer :-)
If you want a very simple version of it you could define an implicit class like:
implicit class TuppleAdd(t: (Int, Int)) {
def +(p: (Int, Int)) = (p._1 + t._1, p._2 + t._2)
}
(1, 1) + (2, 2) == (3, 3)
// update1, more generic version for numbers:
So this is the simplest version, defined only for Ints, we could generify it for all numeric values using Scala's Numeric:
implicit class Tupple2Add[A : Numeric, B : Numeric](t: (A, B)) {
import Numeric.Implicits._
def + (p: (A, B)) = (p._1 + t._1, p._2 + t._2)
}
(2.0, 1) + (1.0, 2) == (3.0, 3)
answered Oct 26, 2013 at 12:54
Konrad 'ktoso' Malawski
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4 Comments
senia
There is not only
Int in the question. You could improve your answer with math.Numeric like this: implicit class TuppleAdd[A : Numeric, B : Numeric](t: (A, B)) { import Numeric.Implicits._; def +(p: (A, B)) = (p._1 + t._1, p._2 + t._2) }.
Konrad 'ktoso' Malawski
That is true :-) I also thought about a version with a structural type, but let's not go there maybe ;-)
metasim
Does your
+ issue perchance have to do with this?: stackoverflow.com/questions/6906742/…