Briefcase: a special kind of folder in Microsoft Windows, which synchronizes its contents with another briefcase of the same name when detected. Used to keep volatile documents on floppy disks & USB flash drives without constantly copying and pasting the contents of the whole disk every time it moves from workstation to workstation. Like an rsync daemon. Use case: in the studies of software design & architecture, a storyboard sketch, or supposition about what a user expects or how s/he'll behave. E.g.. This would be the initial node of a flowchart, a branch in main(), GUI dialog panes, or some interaction of user with program. Additionally, analysis of hostile users and newbies ("misuse case"). I am still moribund ("deadlocked," or "sick to death") by a headache that has become cerebral palsy. I have been unable to concentrate on my plans this year. Speaking of contributions to science, you can find my (literally) auriferous portfolio at the magnanimous MediaFire (they're not just for pirates!): https://www.mediafire.com/folder/kr2bjyn1k3gjr/mlptk-recent (Download & read the CARGO-MANIFEST.TXT to ascertain the contents of the archives you seek.) WARNING: ADULTS ONLY. (Explicit sexual content.) Videlicet is still kind of broken. DiffWalk, too, may be faulty. The hyperlink will lead you to a MediaFire directory. I have added new archives (for bandwidth conservationists). The file CARGO-MANIFEST.TXT describes all the contents: _download and read it first_ if you want to know what's in them there archives, which total over one hundred Megabytes, &/or retrieve your preference. What's new: kanamo & transl8 (in MLPTK), Mutate-o-Matic, Videlicet, & DiffWalk. (I said MLPTK was officially dead, but will I let it rest? How about no...) Archivists curating art galleries downloaded from social networks will love Videlicet, which solves the vexing twin problems of automatic attribution and re-configurable data mining. (For those pesky copy protection mechanisms. Videlicet.py easily cuts through Web galleries and markup up to 1/4" thick.) I even threw in the exprimental upnnas: yea, truly this is an epic day. (^- That line alludes to one of the _Juicy Cerebellum_'s author's asides.) The remainder of this briefing describes the salient points of a Python script I wrote to automatically collate issues of my portfolio. Long story short: "diff." Because the large size of the archives I upload has become problematic, I have established a ramshackle mechanism to prepare smaller files for anyone concerned about bandwidth conservation. (MediaFire reports only two Gigabytes since last year, which is no big deal, but I certanly wasn't helping. Also I couldn't think of much else to do.) In case you cared, the usual issues with bandwidth are constriction & latency: to reuse Senator Ted Stevens' "tubes" metaphor, how wide the tube is and how long it is, and either of these can alter an observer's perception of the pressure of fluid forced through the pipe. "When the tubes get full, things can't get through" -- like dead bodies, or the new episode of Veep. Metaphorically one half of this mechanism is a portable diff utility: DiffWalk. The other half is a shell script that identifies changes to the directory tree. Neither is aught remarkable but why don't I talk your ear off about them anyway? Diff is a program similar to cmp, used to compare two files and describe their discrepancies. In common use on Unixlike systems, it is employed to create patch files that require less time to transmit via point-to-point telecommunication than would be needed to transmit the whole file whenever it changed. Because it is so useful an algorithm, and because I've never seen one for Windows (except in the Berkeley Utilities), I made (but didn't test) a portable one in Python. DiffWalk is a walking collater that creates patches similar to diff's. Although the two are not interoperable, they operate in the same manner: by determination of where the files differ and description of the differences. Therewith, a "new" file can be reconstructed from an "old" file plus a patch -- hypothetically, with according decrease of network bandwidth load. Although the script is a few hundreds of lines long, the scanner (the part that goes through the file looking for the interesting bits: such as, in this case, the positions where the new file differs from the old) is one tenth that size. As you've observed in my other software, I do without proper parsers & grammar. This renders my work brief, vulgar, and full of bugs, but sometimes legible. def diff (old_lines, new_lines): #fmt: old_offset old_lines new_lines\nlines\n patch_file = [ patch_copacetic_leadin ]; scan_line = ""; # Compute MD5 checksums for both files... old_md5sum = hashlib.md5(); for line in old_lines: old_md5sum.update(line); old_md5sum = old_md5sum.hexdigest(); scan_line = "%s\t" % (old_md5sum); new_md5sum = hashlib.md5(); for line in new_lines: new_md5sum.update(line); new_md5sum = new_md5sum.hexdigest(); if new_md5sum == old_md5sum: return None; # same file? then no patch req'd. scan_line += "%s\n" % (new_md5sum); patch_file.append(scan_line); # Second line: old_md5 new_md5 oi = 0; ol = len(old_lines); ni = 0; nl = len(new_lines); tally = 0; scan_line; unique_new_lines = set(new_lines) - set(old_lines); while ni < nl: # 2 phases: scan "same" lines, then diff lines oi = 0; tally = 0; while oi < ol and old_lines[oi] != new_lines[ni]: oi += 1; scan_line = "%d\t" % (oi); #Index in "old" file to cat some of its lines while oi < ol and ni < nl and old_lines[oi] == new_lines[ni]: tally += 1; ni += 1; oi += 1; scan_line += "%d\t" % (tally); # Number of lines to cat from "old" file tally = 0; next_ni = ni; while ni < nl and new_lines[next_ni] in unique_new_lines: tally += 1; next_ni += 1; scan_line += "%d\n" % (tally); # Number of lines to cat from "new" file patch_file.append(scan_line); patch_file.extend(new_lines[ni : next_ni]); ni = next_ni; # end while (scan the files, outputting the patch protocol format) return patch_file; # end function diff: returns diff-style patches as writelines() compatible lists Concise and transpicuous: 1. Tally runs of lines that already existed in the old file. (Scan phase.) 2. Tally runs of lines that do not exist in the old file. (Diff phase.) 3. Print a patch format that permits ordered reconstitution of the lines. 4. Repeat until the entire new file can be reconstructed from patch + old. Here, Python's set()s abstract away a tedious series of repetitive scans. Without set or a like data type, I'd have to either hash the "old" file's lines myself (and waste time writing another binary tree) or loop through it all again and again for each line of the new file. (That would be due to the fact that, if lines had been moved about instead of simply moved apart by interjection, then a lockstep scanner would mistakenly skip some and the patch file would be larger.) There is no capacity to patch binary files, but DW still detects when they have changed, and will write a copy into the patch directory. I assume that changes to binary files are due to transcoding, and therefore the patch'd be just as big -- some kinds of binary files, such as SQL databases, don't behave this way and can be patched in the same manner as I patch text files, but I don't use them. (If you extend the algorithm to databases or executables, don't forget to review the pertinent file formats and open the files in binary mode. :) The rest of the script is a wrapper handling directory traversal and file I/O. As `info diff` artfully states, "computer users often find occasion to ask how 2 files differ." The utility of a script like DiffWalk is therefore not limited to patching, but compression protocol is its primary employment on my system. (I still use `diff` for quotidian difference queries because DW isn't in my $PATH.) Likewise, the automatic collation of updates, such as moved and deleted files, is a pleasant amelioration to the task of finding what's changed in an archive since the last published edition. DiffWalk now handles these tasks for me. If you'd like a better solution to the "Briefcase Problem" (how to synchronize files across multiple installations with minimal time and fuss), don't forget to stop by the manual pages for "diff", "patch", and "rsync".
Ubuntu Linux: the Wal-Mart(TM) Frontier. These are the voyages of the Spacecar Grosvenor. Its continuing mission: to allocate new structs & new classes, unite all people within its nation, and leak where memory has never leaked before. Of the numerous Linux installations ("distributions"), I've used Ubuntu Linux (published by Canonical Inc.) most. It contains the Linux kernel, the GNU core utilities, and several other items of interest such as an automagically-configured graphical user interface. It is extraordinarily user-friendly, to the point of feeling constrictive. (The desktop environment has changed since version 11: users now cannot reconfigure the taskbar or workspaces. The repository wants to be a dime-store, too, and although a potentially lucrative storefront I miss the simplicity of Synaptic.) Its installation procedure is simple: download a Live CD image from Canonical's Web site, burn it to a CD-R or RW (these days, you might even need a DVD), and reboot your machine with the disk inserted. (Don't forget to tell the BIOS -- er whatchamacallit, the Extended Firmware Interface -- to boot from CD.) You'll be presented with an operable temporary login. Thence you can install the OS. Also available from this interface was an option to create a USB startup disk, but it has been removed in recent revisions of Ubuntu: previously, using VirtualBox or any similar virtual machine, the user could run the LiveCD & make a startup USB without even rebooting out of their present operating environment, which was useful on old machines whose optical drives had failed. You can still "Install" to the USB key, but it boots slowly & you can't install it from there to a box. The installation wizard is a no brainer: "install alongside Windows." Easy! And it usually doesn't cause your existing Windows system to go up in smoke, either. However, to install Ubuntu more than once per box, you must repartition manually (and may also need to change grub: see /boot/grub and /etc/grub.d). Gparted is included within the live disc images, but must be retrieved again after install. If you'd like to make intimate friends with the manual pages, and discover where primary partitions go when they die, you can install with less assistance. This lets you specify partitions in which to mount your home & system directories, in case you'd like to keep them segregated. (That's probably a great idea, but I never do.) You can also create and specify swap partitions: which are employed as virtual memory and, I suspect, for hibernation and hybrid suspension. About file systems: I typically use FAT32, NTFS, ext4, and ext2. (Total newbie.) FAT32 is elderly and fragile. It's used for boot/EFI partitions, 3DS & 3GPs. NTFS is Microsoft's modern FS. Withstands some crashes, but has no fsck module. ext2 & ext4 are Linux's. ext4 journals. ext2 permits file undeletion (PhotoRec). The extended 4 system is harder to kill than a cockroach on steroids, so I tend to prefer it anywhere near the heart of my archives. I use ext2 | NTFS for USBs. Be very careful not to destroy your existing data when repartitioning the drive. Any such operation carries some risk; back up anything important beforehand. One way to backup is to prepare an empty HDD (or any medium of equal / greater size) and dump the complete contents of the populated disk into the empty one: dd if=/dev/sda of=/dev/sdb status=progress (Where sda is the populated disk, and sdb the empty backup disk.) Similar can be accomplished by dd'ing one of your partitions (/dev/sda1) into a disk or a file, then dd'ing the image back onto a partition of equal size. Disk image flashing is a simple and popular backup method for local machines, sparing you the time to learn rsync (which is more useful in long term remote backups). Far from being an annoying elder sister, dd is the Linux troll's best friend. Beware the dreaded "write a new boot/system partition" prompt. It bricked me. The problem was because I had set the system to "Legacy Support" boot mode, but the original (now unrecognized) installation was in Extended Firmware Interface mode. I was unable to recover until I had re-flashed several partitions. The usual "new car smell" applies: you'll want to configure whatever settings haven't yet been forbidden to you by your GUI-toting overlords. In Ubuntu 16, access them by clicking the gear and wrench icon on the launcher panel. You can also search for something you're missing by using the Dash (Super, or Windows, key pulls it up: then type), which functions similarly to the apropos command: e.g., instead of Ctrl + Alt + T and then "man -k image", Super key then "image". It will also search your files (and, after plugins, several social media sites). Although the newfangled Dash is convenient, don't forget your terminal emulator: you can easily spend the vast majority of your working time using bash by way of gnome-terminal, without ever clicking your treasured Microsoft IntelliMouse 1.1. In Ubuntu 16, as it has been since Ubuntu 11, Ctrl + Alt + T opens the terminal. Under the directory /usr/share/man/, you will find the on line (interactive) manual. This describes the tools available to you. Begin reading it by opening a terminal window (using Control + Alt + T, or the Super / Windows key and then typing "terminal"), keying the command 'man name_of_manual_page', and pressing the Enter key. In this case, the name of the manual page is the page's archive's filename before the .[0-9].gz extension. Of particular interest: telinit, dd, printf, cat, less, sed, tee, gvfs-trash, mawk, grep, bash (if you're using the Bourne Again Shell, which is default on Ubuntu 16), cp, rm, mv, make, sudo, chroot, chown, chmod, chgrp, touch, gunzip, gzip, zip, unzip, python, g++, apt-get (especially `apt-get source ...`), mount, kpartx, date, diff, charmap (same name on Windows!), basename, zipinfo, md5sum, pdftotext, gnome-terminal (which is _how_ you're using bash), fortune, ffmpeg, aview, dblatex, find, cut, uniq, wc, caesar, rot13, curl, wget, sort, vim, man, tr, du, nautilus, tac, column, head, tail, stat, ls, pwd, pushd, popd, gedit, source-highlight, libreoffice (a Microsoft Office killer), base64, flex, bison, regex, perl, firefox, opera, chromium-browser, konqueror, lynx, virtualbox, apropos, od, hexdump, bless, more, pg, pr, echo, rmdir, mkdir, fsck, fdisk (same name, but different function, in Windows), ln, gdm, gnome-session, dhelp, baobab, gparted, kill, locate, ps, photorec, testdisk, update-grub... (If you haven't some of the above, don't worry. You should already have all you need. Keep in mind that the Ubuntu repository's software is divided in sections some of which contain potentially harmful or non-free software. When venturing beyond the fortified walls of <main>, be cautious: you may be eaten by a grue.) Beneath /usr/share/doc/ or /usr/share/help/ are sometimes additional manuals. If you use Linux, you will have to memorize several manuals, and name many more; especially those of the GNU core utilities, which are a great aid to computing. There's also a software repository to assist you with various computing tasks: To acquire additional software: gnome-software (the orange shopping bag to your left, above the Amazon.com icon), the friendly storefront, will assist you. If you prefer a compact heads-up-display, try the Synaptic Package Manager instead. `apt-get install package-name` works well if you know what you're looking for, as does apt-get source package-name for the ponderously masculine. And, speaking of ponderous masculinity, if you retrieve source code for any of Ubuntu's mainline packages, typically all you need to do is 'cd' into the folder containing the top level of the source tree and then invoke the following: 1. ./configure.sh (You shouldn't need to chmod u+x ./configure.sh to accomplish this.) 2. make (You may need to install additional packages or correct minor errors.) 3. sudo make install This can be abbreviated: ./configure.sh && make && sudo make install Beware that sudo is a potentially dangerous operation. Avoid it if unsure. The && operator, in bash, will only execute the next command if the past command exited with a successful status code (i.e., zero). But I digress. You'll occasionally want to mount your other partitions on Linux's file system, so that you can browse the files you've stored there. With external drives this is as simple as connecting them (watch the output of `tail -f /var/log/*` in a console window to observe the log messages about the procedure), but partitions on fixed disks (or others, 'cause reasons) may not be mounted automagically. So: mount -t fs_type -o option,option,... /dev/sd?? path/to/mount/point/ where the mount point is a directory somewhere in your file system. BTW, mounts that occurred automatically will be on points beneath /media/your_username/. On a dual boot Windows system, I mount -t ntfs -o ro /dev/sda3 ~/Desktop/wintmp often because the NTFS partition is in an unsafe state and won't mount writable. In that case, rebooting to Windows and running chkdsk /f C: from Command Prompt with Administrative privileges will sometimes clear the dirty flag if performed multiple times. (How many times before ntfs-3g mounts writable, seems to vary.) When you've attached external media, via USB etc, safely remove them after use: use the "Safely Remove" menu option in the right-click context menu in Nautilus' sidebar (be careful not to accidentally format the disk). You can also, from a shell (gnome-terminal), `sync && umount /dev/sdb*` (if sdb is the medium). Now that you've got a firm foothold in Ubuntu territory, I hope you can see your house from here 'cause Windows seems to be dying a miserable death of attrition. Don't count it out, though: all the Linuxes are terrible at Flight Simulator.
(I have implemented the Trivial File Transfer Protocol, revision 2, in this milestone snapshot. If you have dealt with reprogramming your home router, you may have encountered TFTP. Although other clients presently exist on Linux and elsewhere, I have implemented the protocol with a pair of Python scripts. You’ll need a Python interpreter, and possibly Administrator privileges (if the server requires them to open port 69), to run them. They can transfer files of size up to 32 Megabytes between any two computers communicating via UDP/IP. Warning: you may need to pull out your metaphorical monkey wrench and tweak the network timeout, or other parameters, in both the client and server before they work to your specification. You can also use TFTP to copy files on your local machine, if for whatever reason you need some replacement for the cp command. Links, courtesy of MediaFire, follow:
Executable source code (the programs themselves, ready to run on your computer): http://www.mediafire.com/file/rh5fmfq8xcmb54r/mlptk-2017-01-07.zip
Candy-colored source code (the pretty colors help me read, maybe they’ll help you too?): http://www.mediafire.com/file/llfacv6t61z67iz/mlptk-src-hilite-2017-01-07.zip
My life in a book (this is what YOUR book can look like, if you learn to use my automatic typesetter and tweak it to make it your own!): http://www.mediafire.com/file/ju972na22uljbtw/mlptk-book-2017-01-07.zip
Title is a tediously long pun on "Pan-Seared Programming" from the last lecture. Key: mechanism to operate an electric circuit, as in a keyboard. Emporium: ein handelsplatz; or, perhaps, the brain. Empyreuma: the smell/taste of organic matter burnt in a close vessel (as, pans). Lignite: intermediate between peat & bituminous coal. Empyreumatic odor. Pignite: Pokémon from Black/White. Related to Emboar & Tepig (ember & tepid). Pygmalion (Greek myth): a king; sculptor of Galatea, who Aphrodite animated. A few more ideas that pop up often in the study of computer programming: which, by the way, is not computer science. (Science isn't as much artifice as record- keeping, and the records themselves are the artifact.) MODULARITY As Eric Steven Raymond of Thyrsus Enterprises writes in "The Art of Unix Programming," "keep it simple, stupid." If you can take your programs apart, and then put them back together like Lego(TM) blocks, you can craft reusable parts. CLASSES A kind of object with methods (functions) attached. These are an idiom that lets you lump together all your program's logic with all of its data: then you can take the class out of the program it's in, to put it in another one. _However,_ I have been writing occasionally for nearly twenty years (since I was thirteen) and here's my advice: don't bother with classes unless you're preparing somewhat for a team effort (in which case you're a "class" actor: the other programmers are working on other classes, or methods you aren't), think your code would gain from the encapsulation (perhaps you find it easier to read?), or figure there's a burning need for a standardized interface to whatever you've written (unlikely because you've probably written something to suit one of your immediate needs: standards rarely evolve on their own from individual effort; they're written to the specifications of consortia because one alone doesn't see what others need). Just write your code however works, and save the labels and diagrams for some time when you have time to doodle pictures in the margins of your notebook, or when you _absolutely cannot_ comprehend the whole at once. UNIONS This is a kind of data structure in C. I bet you're thinking "oh, those fuddy- duddy old C dinosaurs, they don't know what progress is really about!" Ah, but you'll see this ancient relic time and again. Even if your language doesn't let you handle the bytes themselves, you've got some sort of interface to them, and even if you don't need to convert between an integer and four ASCII characters with zero processing time, you'll still need to convert various data of course. Classes then arise which simulate the behavior of unions, storing the same datum in multiple different formats or converting back and forth between them. (Cue the scene from _Jurassic Park,_ the film based on Michael Crichton's book, where the velociraptor peeks its head through the curtains at a half-scaffolded tourist resort. Those damn dinosaurs just don't know when to quit!) ACTUALLY, VOID POINTERS WERE WHAT I WAS THINKING OF HERE The most amusing use of void*s I've imagined is to implement the type definition for parser tokens in a LALR parser. Suppose the parser is from a BNF grammar: then the productions are functions receiving tokens as arguments and returning a token. Of course nothing's stopping you from knowing their return types already, but what if you want to (slow the algorithm down) add a layer of indirection to wrap the subroutines, perhaps by routing everything via a vector table, and now for whatever reason you actually _can't_ know the return types ahead of time? Then of course you cast the return value of the function as whatever type fits. ATOMICITY, OPERATOR OVERLOADING, TYPEDEF, AND WRAPPERS Washing brights vs darks, convenience, convenience, & convenience, respectively. Don't forget: convenience helps you later, _when_ you review your code. LINKED LISTS These are a treelike structure, or should I say a grasslike structure. I covered binary trees at some length in my fourth post, titled "On Loggin'." RECURSION The reason why you need recursion is to execute depth-first searches, basically. You want to get partway through the breadth of whatever you're doing at this level of recursion, then set that stuff aside until you've dealt with something immensely more important that you encountered partway through the breadth. Don't confuse this with realtime operating systems (different than realtime priority) or with interrupt handling, because depth-first searching is far different than those other three topics (which each deserve lectures I don't plan to write). REALTIME OPERATING SYSTEMS, REALTIME PRIORITY, INTERRUPT HANDLING Jet airplanes, video games versus file indexing, & how not to save your sanity. GENERATORS A paradigm appearing in such pleasant languages as Python and Icon. Generators are functions that yield, instead of return: they act "pause-able," and that is plausible because sometimes you really don't want to copy-and-paste a block of code to compute intermediate values without losing execution context. Generators are the breadth-first search to recursion's depth-first search, but of course search algorithms aren't all these idioms are good for. Suppose you wanted to iterate an N-ary counter over its permutations. (This is similar to how you configure anagrams of a word, although those are combinations -- for which, see itertools.combinations in the Python documentation, or any of the texts on discrete mathematics that deal with combinatorics.) Now, an N-ary counter looks a lot like this, but you probably don't want a bunch of these... var items = new Array(A, B, C, D, ...); // ... tedious ... var L = items.length; // ... lines ... var nary = new Array(L); // ... of code ... for (var i = 0; i < L; nary[i++] = 0) ; // ... cluttering ... for (var i = L - 1; i >= 0 && ++nary[i] == L; // ... all ... nary[i--] = ((i < 0) ? undefined : 0) // ... your other ... ) ; // end for (incrementation) // ... computations ... ... in the middle of some other code that's doing somewhat tangentially related. So, you write a generator: it takes the N-ary counter by reference, then runs an incrementation loop to update it as desired. The counter is incremented, where- upon control returns to whatever you were doing in the first place. Voila! (This might not seem important, but it is when your screen size is 80 by 24.) NOODLES AND DOODLES, POMS ON YOUR POODLES, OODLES AND OODLES OF KITS & CABOODLES (Boodle (v.t.): swindle, con, deceive. Boodle (n.): gimmick, device, strategy.) Because this lecture consumed only about a half of the available ten thousand characters permissible in a WordPress article, here's a PowerPoint-like summary that I was doodling in the margins because I couldn't concentrate on real work. Modularity: perhaps w/ especial ref to The Art of Unix Programming. "K.I.S.S." Why modularity is important: take programs apart, put them together like legos. Data structures: unions, classes. Why structures are important: atomicity, op overloading, typedefs, wrappers. linked lists: single, double, circular. Trees. Binary trees covered in wp04?? recursion: tree traversal, data aggregation, regular expressions -- "bookmarks" Generators. Perhaps illustrate by reference to an N-ary counter? AFTER-CLASS DISCUSSION WITH ONE HELL OF A GROUCHY ETHICS PROFESSOR Suppose someone is in a coma and their standing directive requests you to play some music for them at a certain time of day. How can you be sure the music is not what is keeping them in a coma, or that they even like it at all? Having experienced death firsthand, when I cut myself & bled with comical inefficiency, I can tell you that only the dying was worth it. The pain was not, and I assure you that my entire sensorium was painful for a while there -- even though I had only a few small lacerations. Death was less unpleasant with less sensory input. I even got sick of the lightbulb -- imagine that! I dragged myself out of the lukewarm bathtub to switch the thing off, and then realized that I was probably not going to die of exsanguination any time soon and went for a snack instead. AFTER-CLASS DISCUSSION WITH ONE HELL OF A GROUCH "You need help! You are insane!" My 1,000 pages of analytical logic versus your plaintive bleat.