We've already got enough definitions of closures flying around without also calling all functions closures. Why not be precise and say that you have a method that takes a function as a parameter?
You can provide that function via any expression that yields a function, including but not limited to a lambda expression (one containing =>). A lambda expression can close over its scope, i.e., forming a closure, meaning that any values, mutated or otherwise, in its scope can be seen from within the lambda expression. The takeaway is that you don't need to know any of this crap (and a lot of other crap we all already know from Java) if you're not performing side effects. On Jul 27, 2012 11:13 AM, "Kevin Wright" <[email protected]> wrote: > You can certainly capture/"close over" the surrounding environment with > any Scala anonymous function. So you can say quite correctly state that > any method accepting a function will accept a closure. > > As to whether or not you must actually exercise this capability before > you're allowed to call it a closure - I guess that's a matter of semantics. > > Going on the definition that you must "use it or lose it", then your > example is a closure, but probably not in the way you're thinking: > > - {y+= 1; println} is evaluated. It adds one to y and returns a > String=>Unit function > - This function is then executed within the for(x <- 1 to 10)comprehension > > At first glance, nothing is obviously captured from the surrounding > environment. But... println is about as impure as you can get, working by > pure side effect; it has behaviour that depends very much on the > surrounding system. > > > Don't believe me? Then try this: > > def foo(): Unit = { > var y = 0 > 1 to 10 map {y+= 1; println} > println(y) > } > > foo() > System.setOut(someOtherPrintStream) > foo() > > > > > On 27 July 2012 14:30, Josh Berry <[email protected]> wrote: > >> On Fri, Jul 27, 2012 at 8:32 AM, Ricky Clarkson >> <[email protected]> wrote: >> > 1 to 10 map { println("Yo"); println } >> > >> > Yo gets printed once, println happens 10 times. Just because you're >> > providing a function doesn't mean you're in a closure. If it was a >> closure >> > (and certain other magic happened to make it well-typed) you'd see Yo 10 >> > times with a blank line between each. >> >> I'm lost. A closure simply means it captures the local environment, >> right? So: >> >> var y = 0 >> 1 to 10 map {y+= 1; println} >> println(y) >> >> Now, I confess I am surprised that it appears this closure is called >> once to get a function from Int => Any. I'm assuming it has always >> been this way in Scala? >> >> Of course, this does as expected, and looks similar. >> >> for (x <- 1 to 10) {y+=1; println("hello")} >> >> Is this is not a closure, as well? >> >> -- > You received this message because you are subscribed to the Google Groups > "Java Posse" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/javaposse?hl=en. > -- You received this message because you are subscribed to the Google Groups "Java Posse" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/javaposse?hl=en.
