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    Why doesn’t this one compile? http://nurkiewicz.github.io/talks/2014/scalar/#/18

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      The second one takes a call-by-name parameter, which is a different type than an Int.

      scala> def foo(x: => Int): Int = x
      foo: (x: => Int)Int

      scala> foo _
      res3: (=> Int) => Int = <function1>

      foreach takes as an argument a function (Int) => Unit, and (=> Int) => Unit is not of type (Int) => Unit.

      Call by name parameters are a little hack-y and aren’t really first class in scala. They can make some APIs cleaner, but they are currently restrictive. See SI-5787.