Specs

unpipe(t()) :: [t()]

Breaks a pipeline expression into a list.

The AST for a pipeline (a sequence of applications of |>) is similar to the AST of a sequence of binary operators or function applications: the top-level expression is the right-most :|> (which is the last one to be executed), and its left-hand and right-hand sides are its arguments:

quote do: 100 |> div(5) |> div(2)
#=> {:|>, _, [arg1, arg2]}

In the example above, the |> pipe is the right-most pipe; arg1 is the AST for 100 |> div(5), and arg2 is the AST for div(2).

It's often useful to have the AST for such a pipeline as a list of function applications. This function does exactly that:

Macro.unpipe(quote do: 100 |> div(5) |> div(2))
#=> [{100, 0}, {{:div, [], [5]}, 0}, {{:div, [], [2]}, 0}]

We get a list that follows the pipeline directly: first the 100, then the div(5) (more precisely, its AST), then div(2). The 0 as the second element of the tuples is the position of the previous element in the pipeline inside the current function application: {{:div, [], [5]}, 0} means that the previous element (100) will be inserted as the 0th (first) argument to the div/2 function, so that the AST for that function will become {:div, [], [100, 5]} (div(100, 5)).