Stream.Flow._extend._map 

Filter and converter

Only lets elements for which given PartialFinction is defined

The elements are converted to returned type

def all = ~~[Any] + "ABC" + 1 + 22.0 + "DE" + 333F + "F"

all.lp                                     // Prints ~(ABC, 1, 22.0, DE, 333.0, F)

all.collect{
    case s: String if (s.length > 1) => s
}.lp                                       // Prints ~(ABC, DE)

Note. collect always requires double evaluation for each element, so letMap is preferred in many cases

Map multiplier

For every existing element, a mapped stream of elements is inserted into the pipeline

Note. The mapping can return an empty stream, in which case total number of elements might even be reduced

~~(1, 2, 3).flatMap(i => Seq(i * 10, i * 100, i * 1000)).lp

// Output
~(10, 100, 1000, 20, 200, 2000, 30, 300, 3000)

Filter and converter

Only lets elements for which given function returns non empty Opt

The elements are converted to the new type

def all = "ABC" ~+ "1" + "22" + "D" + "333" + "E"

all.letMap(v => if (v.length < 2) \/ else v).lp // Prints: ~(ABC, 22, 333)

all.letMap({
  case s if (s.length >= 2) => s
  case _                    => \/
}).lp                                           // Prints: ~(ABC, 22, 333)

Note: letMap is often a faster alternative to collect with PartialFunction, because it is evaluated just once for each element

Filter and type converter

Only lets elements, which are instances of the given type

Note, the result is mapped to the specified type

def all = ~~[Any] + "1" + 2 + 3.0 + 4l + "5"

all.lp                  // Prints ~(1, 2, 3.0, 4, 5)

all.letType[String].lp  // Prints ~(1, 5)

Element conversion

Converts every element in the pipeline with given function

(1 to 5).all.map( _ / 2.0).lp  // Prints ~(0.5, 1.0, 1.5, 2.0, 2.5)

Element cast

Casts the pipeline elements into the type specified

def all: ~[Any] = ~~[Any] + 1 + 2 + 3

all.mapCast[Int].lp   // Prints: ~(1, 2, 3)

Note. The cast will not fail immediately, and if there is a problem, it will come up later during pumping action