[Technology] Recursion

A friend was asking whether I had a great way to explain recursion.  I had better ways back when I was first learning it, but now it's a bit too implicit.  However, here's an approximation of how I liked to look at it initially.  It's programming centric, in terms of stack frames, but the helpful principle to me was expanding a function as the window into another function, and in particular, into the function of itself.

Recursion note

[Technology] Visitor Pattern

A friend mentioned topics in CS they are dealing with recently.  One is the Visitor pattern.  One of its goals is to keep categories of logic outside of objects they apply to, but which they are conceptually distinct from.  Objects representing animals don't directly care about the logic of saving.   Instead, you get a separate object representing the animal and one representing the logic of saving; this logic-based object is a visitor which will visit the animal to do its work.

How they interact is neat.  They are both passed to one another, which is a degree of coupling I generally try to avoid.  The subject (the animal) has an accept method, which it uses to accept its visitor (the logical object).  The visiting logical object has a visit method, which the subject passes itself to.  The visit method on the logical object then performs its logic on the subject.  Yay!

One of the consequences is a plurality of methods that come into existence to handle the different combinations of subject and visitor.   These blocks of logic are a little unavoidable, so the visitor pattern doesn't really help you reduce the amount of code.  Instead, it just helps you organise it and it simplifies its usage.   Without the visitor pattern, you might have each animal including the logic within its class as methods.  With the visitor pattern, each subject has a trivial function that just passes itself to a visiting visitor that it has accepted.  The visitor will have a different visit () method for each potential subject it might work on, so the subject passing itself to the visitor's visit () helps identify which logic to use.

This vague explanation is elaborated on in this Wikipedia article.

Dieses Blog durchsuchen


#Technology #GNOME gnome gxml fedora bugs linux vala google #General firefox security gsoc GUADEC android bug xml fedora 18 javascript libxml2 programming web blogger encryption fedora 17 gdom git emacs libgdata memory mozilla open source serialisation upgrade web development API Spain containers design evolution fedora 16 fedora 20 fedora 22 fedup file systems friends future glib gnome shell internet luks music performance phone photos php podman preupgrade tablet testing typescript yum #Microblog Network Manager adb apache art automation bash brno catastrophe css data loss debian debugging deja-dup disaster docker emusic errors ext4 facebook fedora 19 gee gir gitlab gitorious gmail gobject google talk google+ gtk html libxml mail microsoft mtp mysql namespaces nautilus nextcloud owncloud picasaweb pitivi ptp python raspberry pi resizing rpm school selinux signal sms speech dispatcher systemd technology texting time management uoguelph usability video web design youtube #Tech Air Canada C Electron Element Empathy Europe GError GNOME 3 GNOME Files Go Google Play Music Grimes IRC Mac OS X Mario Kart Memento Nintendo Nintendo Switch PEAP Selenium Splatoon UI VPN Xiki accessibility advertising ai albums anaconda anonymity apple ask asus eee top automake autonomous automobiles b43 backup battery berlin bit rot broadcom browsers browsing canada canadian english cars chrome clarity comments communication compiler complaints computer computers configuration console constructive criticism cron cropping customisation dataloss dconf debug symbols design patterns desktop summit development discoverability distribution diy dnf documentation drm duplicity e-mail efficiency email english environment estate experimenting ext3 fedora 11 festival file formats firejail flac flatpak forgottotagit freedom friendship fuse galaxy nexus galton gay rights gdb german germany gimp gio gjs gnome software gnome-control-center google assistant google calendar google chrome google hangouts google reader gqe graphviz growth gtest gtg gvfs gvfs metadata hard drive hard drives hardware help hp humour ide identity instagram installation instant messaging integration intel interactivity introspection jabber java java 13 jobs kernel keyboard language language servers languages law learning lenovo letsencrypt libreoffice librpm life livecd liveusb login lsp macbook maintainership mariadb mario matrix memory leaks messaging mounting mouse netflix new zealand node nodelist numix obama oci ogg oggenc oh the humanity open open standards openoffice optimisation org-mode organisation package management packagekit paint shedding parallelism pdo perl pipelight privacy productivity progress progressive web apps pumpkin pwa pyright quality recursion redhat refactoring repairs report rhythmbox rust sandboxes scheduling screenshots self-navigating car shell sleep smartphones software software engineering speed sql ssd synergy tabs test tests themes thesis tracker travel triumf turtles tv tweak twist typing university update usb user experience valadoc video editing volunteering vpnc waf warm wayland weather web apps website wifi wiki wireless wishes work xinput xmpp xorg xpath
Powered by Blogger.