In Scala programming use an anonymous function is a usual thing . when i decide to creat a vector as out put of an anonymous function from two different ways
way one :
var hold1=(1 to 5).map(_*2)
way two:
var hold2=(1 to 5).map(2*)
I want to know what is the difference between those two declaration ?
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2 Answers
In short - they are exactly the same. First approach:
var hold1 = (1 to 5).map(_*2)
Let's rewrite this another way to demonstrate what's really happening under the hood (no syntactic sugar)
var hold1 = (1 to 5).map(number => number.*(2))
Second approach:
var hold2 = (1 to 5).map(2*)
Rewrite again:
var hold2 = (1 to 5).map(number => 2.*(number))
All that is happening is in first way are invoking the * def on the number 2 and in the second way we are invoking the * def on the number.
3 Comments
Rob Starling
it might be interesting to look at the generated code, however.
_ * 2 almost certainly creates an anonymous lambda, but 2 * might not.
Jörg W Mittag
They are only exactly the same if you assume that
Int.* is symmetric! That is not true in the general case.
Jon Taylor
Why does the second version which calls the
.* method not require the _? Should it not be (1 to 5).map(2 * _) ?Both are exactly same. You can use underscore character in many different ways. Refer this link for more details.
