The previous representation was very hard to compose
and very often required the AST nodes to be created
manually.
The current approach is easier to compose because
the node is represented as any other operator as long
as it is wrapped in parentheses.
For example, imagine we have pairs of patterns and
the code to be executed for that pattern, and we want
to inject them into a case. It can now be writen as:
pairs = Enum.map pairs, fn { pattern, expr } ->
quote do: (unquote(pattern) -> unquote(expr))
end
quote do
case unquote(condition), do: unquote(pairs)
end
Compare to the previous implementation:
pairs = Enum.map pairs, fn { pattern, expr } ->
{ [pattern], [], expr }
end
pairs = { :->, [], pairs }
quote do
case unquote(condition), do: unquote(pairs)
end
José Valim
51aef55c83