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lembark (6) [Avatar] Offline
I'm not really seeing how foldLeft differs from reduce (with the possible change that the accumulated value is passed vs. stored internally). Be nice to see if either (a) fL is a synonym for "reduce" or (b) what really makes it different usen used with FP.
aslam.khan (50) [Avatar] Offline
Re: Be interesting to see how foldLeft differs from reduce (p.85+)
That is a very good question. The way that I introduced it, reduce is a special form of fold. I wanted to avoid the subtle difference at this point, but I think I will have to include it since it is causing some confusion.

So, in advance of the correction, and to clear the confusion for you...

A fold can take a list of any type, perform an operation on it, and output something of a completely different type. For example, take a list of integers and output a List of string values of the integers:
List(1,2,3,4,5).foldLeft(List[String]()) { (a, b) => b.toString :: a }

A reduce, on the other hand, will behave just like a fold but is constrained in producing an output of the same type as the that of the input collection (or a supertype thereof).

List(1,2,3,4,5).reduceLeft { (a, b) => a + b }