Chaining

Symmetry of chaining.

Chaining by last parameter

Symbol: |>
Works as transformation rule.
It takes the result of expression and puts it as the last parameter to the next expression.

If you want to use such functional programming libraries as rambda you will find |> operator very useful.
In the following example phone constant equals 'IPHONE':

=-> 'ramda' R

= electronics ::

:

title ' iPhone '

type 'phone'

= phones |>

electronics

R.find

R.propEq 'type' 'phone'

R.prop 'title'

R.toUpper

R.trim

Chaining by first parameter

Symbol: <|
Works as transformation rule.
It takes the result of the expression and puts it as the second parameter to the next expression.

Because of "Polish notation" application order it's hard to do chains with functions stored in maps.

Look how ugly it looks:

= sum .reduce

.filter

.map (:: 1 2 3) (-> x (+ x 1))

-> x (> x 2)

-> (x y) (+ x y)

0

With <| it can be rewritten as:

= sum <| (:: 1 2 3)

.map (-> x (+ x 1))

.filter (-> x (> x 2))

.reduce (-> (x y) (+ x y)) 0