How to make a tuple with a sequence from sequence of tuples?

Question

I have a collection of tuples:

Seq(("foo", "bar3"), ("foo", "bar1"), ("foo", "bar2"))

How do I apply such a function that I get

("foo", Seq("bar1", "bar2", "bar3"))

I just cannot wrap my head around this. I am new to functional programming so I was thinking about some sort of folding or aggregating.

Will the first element of the tuple always have the same value? Or do you want to collect together all the second elements that share the same value of the first element? And is the order of the Seq of second elements important? I note it isn't the order of the input sequence, and is sorted, but is that accidental or do you want it sorted? — The Archetypal Paul
– The Archetypal Paul, Commented Jul 6, 2016 at 15:06
@TheArchetypalPaul The order is not important. I want to collect together all the second elements that share the same value of the first element. — carpenter
– carpenter, Commented Jul 6, 2016 at 15:14

Sergii Lagutin · Accepted Answer · 2016-07-06 13:09:31Z

2

I guess your solution looks like this:

val seq = Seq(("foo", "bar3"), ("foo", "bar1"), ("foo", "bar2"))
seq.groupBy(_._1)
  .mapValues(_.map(_._2))

edited Jul 6, 2016 at 13:09

answered Jul 6, 2016 at 12:49

Sergii Lagutin

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2 Comments

Sergii Lagutin Over a year ago

@AlexandrDorokhin partially I agree with you. Made minor improvements in code

carpenter Over a year ago

@AlexandrDorokhin But it works well, even with structure like Seq((foo, foo1, bar1),(foo, foo1, bar2),... (with replacing _._2 in the last line of code with custom mapping.

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