3.5. Pipeline Operator
Chaining computations in Letlang
Chaining computations can sometimes be awkward.
When you have quite a number of steps, each requiring the output of the previous step, the code can become hard to read.
list(map( lambda x: x * 2, filter( lambda x: x % 2 == 0, range(10, 20) ) ))
This Python code will produce the following list:
[20, 24, 28, 32, 36]
Elixir, F#, R (and probably many other languages) all have a solution for this: the pipeline operator.
A pipeline will transform some data by applying sequentially computations, each depending on the result of the previous one, and producing an output that will be forwarded to the next.
If python had a pipeline operator (
|> for example), the previous code could
be rewritten as:
range(10, 20) |> filter(lambda x: x % 2 == 0) |> map(lambda x: x * 2) |> list()
Which is definitely clearer.
Here is how it works in the following languages:
|Elixir||Injects the lefthand-side value as first argument of the righthand-side function call|
|F#||Injects the value on one side to the function call on the opposite side|
|R||Injects the lefthand-side value as first argument of the righthand-side function call|
In Letlang, the pipeline operator mimics the one from Elixir:
x |> add(5) |> mul(2) # equivalent to mul(add(x, 5), 2)