__get_iter is a bit of a mess. It handles both creating a node iterator AND printing functionality.
filter_ tells us to only print nodes meeting some user-specified property. filter_ is a function. You input a node into filter_ and filter returns true (print the node) or false (don't print the node). Do not get me wrong, that's a perfectly reasonable thing to want to do. I only mention what filter_ is so that we can see how to decouple making node iterators and printing.
key and reverse tell us how to order the nodes for printing purposes. reverse is a Boolean, which says to print the nodes in reverse order. key allows more complicated node orderings than a mere reversal.
dt is a container of three elements:
dt_vline
dt_line_box
dt_line_cor.
Each element is a string of characters used in printing:
dt_vline is something like "|"
dt_line_box is something like "|-- "
dt_line_cor is something like '+-- '
The code would be much cleaner if the back-end function which constructs and returns a node iterator knew nothing about printing, and the printing functionality used node iterators without knowing about filter_key or reverse
The function with generates a node iterator would use filter_key and reverse but not dt, dt_vline, dt_line_box, dt_line_cor.
After generating a node-iterator you pass the node-iterator to the printing function. The printing function does not know if the iterator it just received loops over ALL nodes, SOME of the nodes, nodes in forward order, nodes in backward order, etc... The printer doesn't need to know. It just needs a node iterator.
__get_iteris a bit of a mess. It handles both creating a node iterator AND printing functionality.filter_tells us to only print nodes meeting some user-specified property.filter_is a function. You input a node intofilter_and filter returnstrue(print the node) orfalse(don't print the node). Do not get me wrong, that's a perfectly reasonable thing to want to do. I only mention whatfilter_is so that we can see how to decouple making node iterators and printing.keyandreversetell us how to order the nodes for printing purposes.reverseis a Boolean, which says to print the nodes in reverse order.keyallows more complicated node orderings than a mere reversal.dtis a container of three elements:dt_vlinedt_line_boxdt_line_cor. Each element is a string of characters used in printing:dt_vlineis something like "|"dt_line_boxis something like "|-- "dt_line_coris something like '+-- 'The code would be much cleaner if the back-end function which constructs and returns a node iterator knew nothing about printing, and the printing functionality used node iterators without knowing about
filter_keyorreverseThe function with generates a node iterator would use
filter_keyandreversebut notdt,dt_vline,dt_line_box,dt_line_cor.After generating a node-iterator you pass the node-iterator to the printing function. The printing function does not know if the iterator it just received loops over ALL nodes, SOME of the nodes, nodes in forward order, nodes in backward order, etc... The printer doesn't need to know. It just needs a node iterator.