White wandering through exercism.io solutions, I just stumbled upon this:
# rows/1, and columns/1 are functions that return lists of columns and rows, respectively
def saddle_points(str) do
for {row, ri} <- Enum.with_index(rows(str)),
{col, ci} <- Enum.with_index(columns(str)),
max = Enum.max(row),
min = Enum.min(col),
min == max,
do: {ri, ci}
end
In my opinion this is a very smart solution to finding saddle points in a matrix (my own was extremely over-engineered). Now that looked at this code, I realize I might not have a good understanding of how for special form works, and what else you can do with it.
I knew that one can specify filters (such as ==, for example) and multiple dependent lists to be read from, e.g.:
for my_list <- list_of_lists,
element <- my_list,
element != 3,
do: element
But this example in the beginning of the post suggests there are more powerful ways of using for:
- Lists may not be dependent at all – I’ve never thought about it,
- One may use assignment (pattern matching), such as
max = Enum.max(row), too – how/why does this even work?
So, my mind is blown, and I just wanted to share this. Also, is there anything else I’m missing from fully understanding the for special form?
