fl-generators v1.0.0

:fuelpump: fl-generators

fl-generators provides a declarative API for creating generators.

const Iter = require('fl-generators');

tunedPianos = Iter.of(instruments).filter(isPiano).map(tune);

Is equivalent to:

const filter = function*(it, g) {
  for (const x of it()) {
    if (g(x)) {
      yield x;
    }
  }
}

const map = function*(it, g) {
  for (const x of it()) {
    yield g(x);
  }
}

tunedPianos = map(filter(instruments, isPiano), tune);

:warning: Notice

Generators are not optimized in V8 or SpiderMonkey. Using generator functions is significantly slower in most situations.

• v8-users - Is there intent to allow optimization of generator functions?
• wingolog - generators in firefox now twenty-two times faster

Iter methods

• cache
• concatAll
• concat
• cycle
• do
• filter
• flatMap
• map
• reduce
• repeat
• run
• scan
• skip
• skipWhile
• slice
• take
• takeWhile
• toArray
• zip

Examples

const Iter = require('fl-generators');

Iter.range(0, 6)
  .filter(n => n % 2 === 0)
  .map(n => n + 1)
  .flatMap(n => [n - 1, n, n + 1])
  .reduce((x, y) => x + y, 0);

// filter 0
// map 0
// flatMap 1
// filter 1
// filter 2
// map 2
// flatMap 3
// filter 3
// filter 4
// map 4
// flatMap 5
// filter 5
// filter 6
// map 6
// flatMap 7
// reduce 48

Array.from({ length: 7 }, (_, i) => i)
  .filter(n => n % 2 === 0)
  .map(n => n + 1)
  .reduce((c, n) =>  c.concat([n - 1, n, n + 1]), [])
  .reduce((x, y) => x + y, 0);

// filter 0
// filter 1
// filter 2
// filter 3
// filter 4
// filter 5
// filter 6
// map 0
// map 2
// map 4
// map 6
// flatMap 1
// flatMap 3
// flatMap 5
// flatMap 7
// reduce 48