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• The best cross platform (portable) arbitrary precision math library

  - by Siu Ching Pong - Asuka Kenji

  Dear ninjas / hackers / wizards, I'm looking for a good arbitrary precision math library in C or C++. Could you please give me some advices / suggestions? The primary requirements: It MUST handle arbitrarily big integers (my primary interest is on integers). In case that you don't know what the word arbitrarily big means, imagine something like 100000! (the factorial of 100000). The precision MUST NOT NEED to be specified during library initialization / object creation. The precision should ONLY be constrained by the available resources of the system. It SHOULD utilize the full power of the platform, and should handle "small" numbers natively. That means on a 64-bit platform, calculating 2^33 + 2^32 should use the available 64-bit CPU instructions. The library SHOULD NOT calculate this in the same way as it does with 2^66 + 2^65 on the same platform. It MUST handle addition (+), subtraction (-), multiplication (*), integer division (/), remainder (%), power (**), increment (++), decrement (--), gcd(), factorial(), and other common integer arithmetic calculations efficiently. Ability to handle functions like sqrt() (square root), log() (logarithm) that do not produce integer results is a plus. Ability to handle symbolic computations is even better. Here are what I found so far: Java's BigInteger and BigDecimal class: I have been using these so far. I have read the source code, but I don't understand the math underneath. It may be based on theories / algorithms that I have never learnt. The built-in integer type or in core libraries of bc / Python / Ruby / Haskell / Lisp / Erlang / OCaml / PHP / some other languages: I have ever used some of these, but I have no idea on which library they are using, or which kind of implementation they are using. What I have already known: Using a char as a decimal digit, and a char* as a decimal string and do calculations on the digits using a for-loop. Using an int (or a long int, or a long long) as a basic "unit" and an array of it as an arbitrary long integer, and do calculations on the elements using a for-loop. Booth's multiplication algorithm What I don't know: Printing the binary array mentioned above in decimal without using naive methods. Example of a naive method: (1) add the bits from the lowest to the highest: 1, 2, 4, 8, 16, 32, ... (2) use a char* string mentioned above to store the intermediate decimal results). What I appreciate: Good comparisons on GMP, MPFR, decNumber (or other libraries that are good in your opinion). Good suggestions on books / articles that I should read. For example, an illustration with figures on how a un-naive arbitrarily long binary to decimal conversion algorithm works is good. Any help. Please DO NOT answer this question if: you think using a double (or a long double, or a long long double) can solve this problem easily. If you do think so, it means that you don't understand the issue under discussion. you have no experience on arbitrary precision mathematics. Thank you in advance! Asuka Kenji

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• Allocation algorithm help, using Python.

  - by Az

  Hi there, I've been working on this general allocation algorithm for students. The pseudocode for it (a Python implementation) is: for a student in a dictionary of students: for student's preference in a set of preferences (ordered from 1 to 10): let temp_project be the first preferred project check if temp_project is available if so, allocate it to them and make the project UNavailable to others Quite simply this will try to allocate projects by starting from their most preferred. The way it works, out of a set of say 100 projects, you list 10 you would want to do. So the 10th project wouldn't be the "least preferred overall" but rather the least preferred in their chosen set, which isn't so bad. Obviously if it can't allocate a project, a student just reverts to the base case which is an allocation of None, with a rank of 11. What I'm doing is calculating the allocation "quality" based on a weighted sum of the ranks. So the lower the numbers (i.e. more highly preferred projects), the better the allocation quality (i.e. more students have highly preferred projects). That's basically what I've currently got. Simple and it works. Now I'm working on this algorithm that tries to minimise the allocation weight locally (this pseudocode is a bit messy, sorry). The only reason this will probably work is because my "search space" as it is, isn't particularly large (just a very general, anecdotal observation, mind you). Since the project is only specific to my Department, we have their own limits imposed. So the number of students can't exceed 100 and the number of preferences won't exceed 10. for student in a dictionary/list/whatever of students: where i = 0 take the (i)st student, (i+1)nd student for their ranks: allocate the projects and set local_weighting to be sum(student_i.alloc_proj_rank, student_i+1.alloc_proj_rank) these are the cases: if local_weighting is 2 (i.e. both ranks are 1): then i += 1 and and continue above if local weighting is = N>2 (i.e. one or more ranks are greater than 1): let temp_local_weighting be N: pick student with lowest rank and then move him to his next rank and pick the other student and reallocate his project after this if temp_local_weighting is < N: then allocate those projects to the students move student with lowest rank to the next rank and reallocate other if temp_local_weighting < previous_temp_allocation: let these be the new allocated projects try moving for the lowest rank and reallocate other else: if this weighting => previous_weighting let these be the allocated projects i += 1 and move on for the rest of the students So, questions: This is sort of a modification of simulated annealing, but any sort of comments on this would be appreciated. How would I keep track of which student is (i) and which student is (i+1) If my overall list of students is 100, then the thing would mess up on (i+1) = 101 since there is none. How can I circumvent that? Any immediate flaws that can be spotted? Extra info: My students dictionary is designed as such: students[student_id] = Student(student_id, student_name, alloc_proj, alloc_proj_rank, preferences) where preferences is in the form of a dictionary such that preferences[rank] = {project_id}

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• PROJECT HELP NEEDED. SOME BASIC CONCEPTS GREAT CONFUSION BECAUSE OF LACK OF PROPER MATERIAL PLEASE H

  - by user287745

  Task ATTENDENCE RECORDER AND MANAGEMENT SYSTEM IN DISTRIBUTED ENVIRONMENT ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Example implementation needed. a main server in each lab where the operator punches in the attendence of the student. =========================================================== scenerio:- a college, 10 departments, all departments have a computer lab with 60-100 computers, the computers within each lab are interconnected and all computers in any department have to dail to a particular number (THE NUMBER GIVEN BY THE COLLEGE INTERNET DEPARTMENT) to get connected to the internet. therefore safe to assume that there is a central location to which all the computers in the college are connected to. there is a 'students attendence portal' which can be accessed using internet explorer, students enter there id and get the particular attendence record regarding to the labs only. a description of the working is like:- 1) the user will select which department, which year has arrived to the lab 2) the selection will give the user a return of all the students name and there roll numbers belonging to that department; 'with a check box to "TICK MARK IF THE STUDENT IS PRESENT" ' 3) A SUBMIT BUTTON when pressed reads the 'id' of the checkbox to determine the "particular count number of the student" from that an id of the student is constructed and that id is inserted with a present. (there is also date and time and much more to normalize the db and to avoid conflicts and keep historic records etc but that you will have to assume) steps taken till this date:- ( please note we are not computer students, we are to select something of some other line as a project!, as you will read in my many post 'i" have designed small websites just out of liking. have never ever done any thing official to implement like this.) * have made the database fully normalized. * have made the website which does the functions required on the database. Testing :- deployed the db and site on a free aspspider server and it worked. tested from several computers. Now the problem please help thank youuuuuuuu a practical demonstration has to be done within the college network. no internet! we have been assigned a lab - 60 computers- to demonstrate. (please dont give replies as 60 computers only! is not a big deal one CPU can manage it. i know that; IT IS A HYPOTHETICAL SITUATION WHERE WE ASSUME THAT 60 IS NOT 60 BUT ITS LIKE 60,000 COMPUTERS) 1a) make a web server, yes iis and put files in www folder and configure server to run aspx files- although a link to a step by step guide will be appreciated)\ ? which version of windows should i ask for xp or win server 2000 something? 2a) make a database server. ( well yes install sql server 2005, okay but then what? just put the database file on a pc share it and append the connection string to the share? ) 3a) make the site accessible from the remaining computers ? http://localhost/sitename ? all users "being operators of the particular lab" have the right to edit, write or delete(in dispute), thereby any "users" who hate our program can make the database inconsistent by accessing te same record and doing different edits and then complaining? so how to prevent this? you know something like when the db table is being written to others can only read but not write.. one big confusion:- IN DISTRIBUTED ENVIRONMENT "how to implement this" where does "distributed environment" come in! meaning :- alright the labs are in different departments but the "database server will be one" the "web server will be one" so whats distributed!?

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• Smart auto detect and replace URLs with anchor tags

  - by Robert Koritnik

  I've written a regular expression that automatically detects URLs in free text that users enter. This is not such a simple task as it may seem at first. Jeff Atwood writes about it in his post. His regular expression works, but needs extra code after detection is done. I've managed to write a regular expression that does everything in a single go. This is how it looks like (I've broken it down into separate lines to make it more understandable what it does): 1 (?<outer>\()? 2 (?<scheme>http(?<secure>s)?://)? 3 (?<url> 4 (?(scheme) 5 (?:www\.)? 6 | 7 www\. 8 ) 9 [a-z0-9] 10 (?(outer) 11 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\)) 12 | 13 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+ 14 ) 15 ) 16 (?<ending>(?(outer)\))) As you may see, I'm using named capture groups (used later in Regex.Replace()) and I've also included some local characters (cšžcd), that allow our localised URL to be parsed as well. You can easily omit them if you'd like. Anyway. Here's what it does (referring to line numbers): 1 - detects if URL starts with open braces (is contained inside braces) and stores it in "outer" named capture group 2 - checks if it starts with URL scheme also detecting whether scheme is SSL or not 3 - starts parsing URL itself (will store it in "url" named capture group) 4-8 - if statement that says: if "sheme" was present then www. part is optional, otherwise mandatory for a string to be a link (so this regular expression detects all strings that start with either http or www) 9 - first character after http:// or www. should be either a letter or a number (this can be extended if you would like to cover even more links, but I've decided to omit other characters because I can't remember a link that would start with some other character 10-14 - if statement that says: if "outer" (braces) was present capture everything up to the last closing braces otherwise capture all 15 - closes the named capture group for URL 16 - if open braces was present, capture closing braces as well and store it in "ending" named capture group First and last line used to have \s* in them as well, so user could also write open braces and put a space inside before pasting link. Anyway. My code that does link replacement with actual anchor HTML elements looks exactly like this: value = Regex.Replace( value, @"(?<outer>\()?(?<scheme>http(?<secure>s)?://)?(?<url>(?(scheme)(?:www\.)?|www\.)[a-z0-9](?(outer)[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\))|[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+))(?<ending>(?(outer)\)))", "${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending}", RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase); As you can see I'm using named capture groups to replace link with an Anchor tag: ${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending} I could as well omit the http(s) part in anchor display to make links look friendlier, but for now I decided not to. Question I would like for my links to be replaced with shortenings as well. So when user copies a very long links (for instance if they would copy a link from google maps that usually generates long links I would like to shorten the visible part of the anchor tag. Link would work, but visible part of an anchor tag would be shortened to some number of characters. Does the replace string support notations like that so I can stil use a singe Regex.Replace() call?

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• Both tab & hover triggered popups problem

  - by carpenter

  I am trying to display divs when hovering over thumb-nails and/or both when tabbing onto them. If I stick to my mouse, the popups seem to work OK - if I start with a tab press I can show the popops also (foward only - no shift + tab yet). Any help getting them to play well together? <script type="text/javascript"> // Note: the below is being run from an onmouseover on a asp:HyperLink at the moment function onhovering_and_tabbingon2() { var active_hover = 0; var num_of_thumb; // set the default focus onto the first thumb-nail and make its popup display document.getElementById('link_no' + active_hover).focus(); // set focus on the first thumb $('#pop' + active_hover).toggleClass('popup'); // show its popup as it is hidden // for when hovering over the thumbs $(".box img").hover( // so as to effect only images/thumb-nails within divs of class=box when hovering over them function () { // test for if the image is a thumb-entry and not a popup image - of class=thumbs2 thumb = $(this).attr('class'); if (thumb != "thumbs2") { // I need to add/toggle the class here to a "div" and not to the image being hovered on, a div with text that corrosponds to the hovered on image though // so grab the number of the thumb_entry - to use to id the div. num_of_thumb = $(this).attr('id').replace('thumb_entry_No', ''); // find the div with id 'pop' + num_of_thumb, and toggleClass on it $('#pop' + num_of_thumb).toggleClass('popup'); // shows the hovered on pic's popup // move the focus to the hovered on pic's a tag ?????? document.getElementById('link_no' + num_of_thumb).focus(); // if the previous popup that was showing was in box2.. if (active_hover == 1 || active_hover% 2 == 1) { $('#pop' + active_hover).toggleClass('popup4_line2'); } else { // remove/toggle the previous active popup's visibility $('#pop' + active_hover).toggleClass('popup'); } // set the new active_hover to num_of_thumb active_hover = num_of_thumb; } }, function () { } ); // same thing again - but for my second row/line of entries/thumb-nails... $(".box2 img").hover( // so as to effect only images/thumbs within divs of class=box2 function () { // test if the image is a thumb-entry and not a popup image thumb = $(this).attr('class'); if (thumb != "thumbs2") { // I need to add the class here to a "div" and not to the image being hovered on, a div that corrosponds to the hovered on image though // so grab the number of the thumb_entry being hovered on, so as to id the div. num_of_thumb = $(this).attr('id').replace('thumb_entry_No', ''); // find the div with id='pop' + num_of_thumb, and toggleClass on it $('#pop' + num_of_thumb).toggleClass('popup4_line2'); // move the focus to the hovered on pic's a tag ?? document.getElementById('link_no' + num_of_thumb).focus(); // if the previous popup that was showing was in box.. // or if the active_hover is even (modulus) if (active_hover == 0 || active_hover % 2 == 0) { $('#pop' + active_hover).toggleClass('popup'); } else { // remove the previous active visible popup $('#pop' + active_hover).toggleClass('popup4_line2'); } // set the new active_hover to num_of_thumb active_hover = num_of_thumb; } }, function () { } ); // todo: I would like to try to show the popups when tabbing through the thumb-nails also // but am lost... document.onkeyup = keypress; // ???? function keypress() { // alert("The key pressed was: " + window.event.keyCode); if (window.event.keyCode == "9") { //alert("The tab key was pressed!"); active_hover = active_hover + 1; // for tabbing into box 2 (odd numbers) if (active_hover == 1 || active_hover % 2 == 1) { // toggle visibility of previous popup $('#pop' + (active_hover - 1)).toggleClass('popup'); // toggle visibility of current popup $('#pop' + active_hover).toggleClass('popup4_line2'); // } else { // for tabbing into box from box2 // toggle visibility of previous popup $('#pop' + (active_hover - 1)).toggleClass('popup4_line2'); // toggle visibility of current popup $('#pop' + active_hover).toggleClass('popup'); // } // ?????? // // if (window.event.keyCode == "shift&9") { } } } } </script>

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• XPath expression with condition on multiple ancestors

  - by Rest Wing

  The application I am developing receives an XML structure similar to following: <Root> <Valid> <Child name="Child1" /> <Container> <Child name="Child2" /> </Container> <Container> <Container> <Child name="Child3"/> <Child name="Child4"/> </Container> </Container> <Wrapper> <Child name="Child5" /> </Wrapper> <Wrapper> <Container> <Child name="Child19" /> </Container> </Wrapper> <Container> <Wrapper> <Child name="Child6" /> </Wrapper> </Container> <Container> <Wrapper> <Container> <Child name="Child20" /> </Container> </Wrapper> </Container> </Valid> <Invalid> <Child name="Child7" /> <Container> <Child name="Child8" /> </Container> <Container> <Container> <Child name="Child9"/> <Child name="Child10"/> </Container> </Container> <Wrapper> <Child name="Child11" /> </Wrapper> <Container> <Wrapper> <Child name="Child12" /> </Wrapper> </Container> </Invalid> </Root> I need to get a list of of Child elements under following conditions: Child is n generation descendant of Valid ancestor. Child may be m generation descendant of Container ancestor which is o generation descendant of Valid ancestor. Valid ancestors for Child element are Container elements as m generation ancestors and Valid element as first generation ancestor. where m, n, o are natural numbers. I need to write following XPath expressions Valid/Child Valid/Container/Child Valid/Container/Container/Child Valid/Container/Container/Container/Child ... as a single XPath expression. For provided example, the XPath expression would return only Child elements having name attribute equal to Child1, Child2, Child3 and Child4. The closest I have come to solution is following expression. Valid/Child | Valid//*[self::Container]/Child However, this would select Child element with name attribute equal to Child19 and Child20. Does XPath syntax supports either optional occurrence of an element or setting condition similar to self in previous example to all ancestors between Child and Valid elements?

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• being able to solve google code jam problem sets

  - by JPro

  This is not a homework question, but rather my intention to know if this is what it takes to learn programming. I keep loggin into TopCoder not to actually participate but to get the basic understand of how the problems are solved. But to my knowledge I don't understand what the problem is and how to translate the problem into an algorithm that can solve it. Just now I happen to look at ACM ICPC 2010 World Finals which is being held in china. The teams were given problem sets and one of them is this: Given at most 100 points on a plan with distinct x-coordinates, find the shortest cycle that passes through each point exactly once, goes from the leftmost point always to the right until it reaches the rightmost point, then goes always to the left until it gets back to the leftmost point. Additionally, two points are given such that the the path from left to right contains the first point, and the path from right to left contains the second point. This seems to be a very simple DP: after processing the last k points, and with the first path ending in point a and the second path ending in point b, what is the smallest total length to achieve that? This is O(n^2) states, transitions in O(n). We deal with the two special points by forcing the first path to contain the first one, and the second path contain the second one. Now I have no idea what I am supposed to solve after reading the problem set. and there's an other one from google code jam: Problem In a big, square room there are two point light sources: one is red and the other is green. There are also n circular pillars. Light travels in straight lines and is absorbed by walls and pillars. The pillars therefore cast shadows: they do not let light through. There are places in the room where no light reaches (black), where only one of the two light sources reaches (red or green), and places where both lights reach (yellow). Compute the total area of each of the four colors in the room. Do not include the area of the pillars. Input * One line containing the number of test cases, T. Each test case contains, in order: * One line containing the coordinates x, y of the red light source. * One line containing the coordinates x, y of the green light source. * One line containing the number of pillars n. * n lines describing the pillars. Each contains 3 numbers x, y, r. The pillar is a disk with the center (x, y) and radius r. The room is the square described by 0 = x, y = 100. Pillars, room walls and light sources are all disjoint, they do not overlap or touch. Output For each test case, output: Case #X: black area red area green area yellow area Is it required that people who program should be should be able to solve these type of problems? I would apprecite if anyone can help me interpret the google code jam problem set as I wish to participate in this years Code Jam to see if I can do anthing or not. Thanks.

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• How to set up port forwarding and firewall settings for torrents using Transmsission on Mac OSX 10.5

  - by Liz

  I have picked up bits of advice here and there on the internet and got someway through this tortuous exercise (after it took 18 hours to download the first torrent I tried yesterday - magnet-link for a film). Where I have got stuck is with configuring the firewall on the Netgear Router but I am not sure if I have caused the problem myself by something else I have done configuring the Mac System Preferences for Security or Networking. I have been following the sections of these instructions that seem to apply, although they are written for a different OSX version (don't know which one, but the screen shots do not match what I see) and I am not wanting to set up my Mac as a server and attending to the parts that apply to port forwarding for Netgear rather than LinkSys: http://homepage.mac.com/car1son/static_port_fwd_intro.html I have been trying to follow these instructions: Instructions for DG834, DG834G, DG824M, FR114W, FM114P, FR114P, FR328S, FVL328, FVS328, FVS338, FVX538, FWAG114, FWG114P, or FVS318v3 These routers do port forwarding by assigning port numbers to a "service" associated with the application you want to run. "Rules" are set for particular services. Rules block or allow access, based on various conditions such as the time of day and the name of the service. To Create a New Inbound or Outbound Rule 1. Submit the router's address in an Internet browser. (The default is 192.168.0.1). 2. Enter the router's username and password. 3. From the main menu, click Security > Rules. 4. Click Add for inbound or outbound traffic, as appropriate to the application you are planning to run. 5. Select the Service. The services the router knows about are listed in the drop down. If the service you want is not listed, add it as described in the next section. 6. Select the Action, for example ALLOW always. 7. For Send to LAN Server, enter the IP address of the local server. Note that this is also the IP address the computers on your LAN will access. 8. For WAN User choose Any, or limit access to particular IP addresses. 9. For Log selection it is reasonable to turn logs on, especially at the beginning when you are unsure of the result of the changes you are making. Later, you may want to set logs to "Never" for performance reasons. 10. Click Apply. As noted in user manual for some models: * Consider using the Dynamic DNS feature on the Advanced menu, so that external users can find your network when the DHCP lease is renewed by your ISP. * If your own LAN server uses DHCP, and your IPs change on rebooting, consider using the Reserved IP Address feature in the LAN IP menu. To Add a Service for These Routers 1. Click Security > Services > Add Custom Service. 2. Enter any name you choose for the service. 3. Select whether the service is to use TCP or UDP. If you are unsure, select both. 4. Enter the lowest port number used by the service. 5. Enter the highest port number used. If the service uses only one port number, enter the same number. 6. Click Apply. There is no "Security - Rules" submenu in the Netgear page, so I have been trying to access "Security - Firewall Rules". I can access everthing else in the Netgear settings as Admin but I cannot get the "Firewall Rules" section to open up. (I am not 100% sure I will know exactly what to do if and when I do get it opened up!) I haven't managed to find though searching the internet any instructions that would seem to apply specifically to what I am trying to achieve, so would be very grateful if someone could either point me in the right direction or give me some advice directly. Best wishes, Liz

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• Is the Unix Philosophy still relevant in the Web 2.0 world?

  - by David Titarenco

  Introduction Hello, let me give you some background before I begin. I started programming when I was 5 or 6 on my dad's PSION II (some primitive BASIC-like language), then I learned more and more, eventually inching my way up to C, C++, Java, PHP, JS, etc. I think I'm a pretty decent coder. I think most people would agree. I'm not a complete social recluse, but I do stuff like write a virtual machine for fun. I've never taken a computer course in college because I've been in and out for the past couple of years and have only been taking core classes; never having been particularly amazing at school, perhaps I'm missing some basic tenet that most learn in CS101. I'm currently reading Coders at Work and this question is based on some ideas I read in there. A Brief (Fictionalized) Example So a certain sunny day I get an idea. I hire a designer and hammer away at some C/C++ code for a couple of months, soon thereafter releasing silvr.com, a website that transmutes lead into silver. Yep, I started my very own start-up and even gave it a clever web 2.0 name with a vowel missing. Mom and dad are proud. I come up with some numbers I should be seeing after 1, 2, 3, 6, 9, 12 months and set sail. Obviously, my transmuting server isn't perfect, sometimes it segfaults, sometimes it leaks memory. I fix it and keep truckin'. After all, gdb is my best friend. Eventually, I'm at a position where a very small community of people are happily transmuting lead into silver on a semi-regular basis, but they want to let their friends on MySpace know how many grams of lead they transmuted today. And they want to post images of their lead and silver nuggets on flickr. I'm losing out on potential traffic unless I let them log in with their Yahoo, Google, and Facebook accounts. They want webcam support and live cock fighting, merry-go-rounds and Jabberwockies. All these things seem necessary. The Aftermath Of course, I have to re-write the transmuting server! After all, I've been losing money all these months. I need OAuth libraries and OpenID libraries, JSON support, and the only stable Jabberwocky API is for Java. C++ isn't even an option anymore. I'm just one guy! The Java binary just grows and grows since I need some legacy Apache include for the JSON library, and some antiquated Sun dependency for OAuth support. Then I pick up a book like Coders at Work and read what people like jwz say about complexity... I think to myself.. Keep it simple, stupid. I like simple things. I've always loved the Unix Philosophy but even after trying to keep the new server source modular and sleek, I loathe having to write one more line of code. It feels that I'm just piling crap on top of other crap. Maybe I'm naive thinking every piece of software can be simple and clever. Maybe it's just a phase.. or is the Unix Philosophy basically dead when it comes to the current state of (web) development? I'm just kind of disheartened :(

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• Representing game states in Tic Tac Toe

  - by dacman

  The goal of the assignment that I'm currently working on for my Data Structures class is to create a of Quantum Tic Tac Toe with an AI that plays to win. Currently, I'm having a bit of trouble finding the most efficient way to represent states. Overview of current Structure: AbstractGame Has and manages AbstractPlayers (game.nextPlayer() returns next player by int ID) Has and intializes AbstractBoard at the beginning of the game Has a GameTree (Complete if called in initialization, incomplete otherwise) AbstractBoard Has a State, a Dimension, and a Parent Game Is a mediator between Player and State, (Translates States from collections of rows to a Point representation Is a StateConsumer AbstractPlayer Is a State Producer Has a ConcreteEvaluationStrategy to evaluate the current board StateTransveralPool Precomputes possible transversals of "3-states". Stores them in a HashMap, where the Set contains nextStates for a given "3-state" State Contains 3 Sets -- a Set of X-Moves, O-Moves, and the Board Each Integer in the set is a Row. These Integer values can be used to get the next row-state from the StateTransversalPool SO, the principle is Each row can be represented by the binary numbers 000-111, where 0 implies an open space and 1 implies a closed space. So, for an incomplete TTT board: From the Set<Integer> board perspective: X_X R1 might be: 101 OO_ R2 might be: 110 X_X R3 might be: 101, where 1 is an open space, and 0 is a closed space From the Set<Integer> xMoves perspective: X_X R1 might be: 101 OO_ R2 might be: 000 X_X R3 might be: 101, where 1 is an X and 0 is not From the Set<Integer> oMoves perspective: X_X R1 might be: 000 OO_ R2 might be: 110 X_X R3 might be: 000, where 1 is an O and 0 is not Then we see that x{R1,R2,R3} & o{R1,R2,R3} = board{R1,R2,R3} The problem is quickly generating next states for the GameTree. If I have player Max (x) with board{R1,R2,R3}, then getting the next row-states for R1, R2, and R3 is simple.. Set<Integer> R1nextStates = StateTransversalPool.get(R1); The problem is that I have to combine each one of those states with R1 and R2. Is there a better data structure besides Set that I could use? Is there a more efficient approach in general? I've also found Point<-State mediation cumbersome. Is there another approach that I could try there? Thanks! Here is the code for my ConcretePlayer class. It might help explain how players produce new states via moves, using the StateProducer (which might need to become StateFactory or StateBuilder). public class ConcretePlayerGeneric extends AbstractPlayer { @Override public BinaryState makeMove() { // Given a move and the current state, produce a new state Point playerMove = super.strategy.evaluate(this); BinaryState currentState = super.getInGame().getBoard().getState(); return StateProducer.getState(this, playerMove, currentState); } } EDIT: I'm starting with normal TTT and moving to Quantum TTT. Given the framework, it should be as simple as creating several new Concrete classes and tweaking some things.

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• Minimum-Waste Print Job Grouping Algorithm?

  - by Matt Mc

  I work at a publishing house and I am setting up one of our presses for "ganging", in other words, printing multiple jobs simultaneously. Given that different print jobs can have different quantities, and anywhere from 1 to 20 jobs might need to be considered at a time, the problem would be to determine which jobs to group together to minimize waste (waste coming from over-printing on smaller-quantity jobs in a given set, that is). Given the following stable data: All jobs are equal in terms of spatial size--placement on paper doesn't come into consideration. There are three "lanes", meaning that three jobs can be printed simultaneously. Ideally, each lane has one job. Part of the problem is minimizing how many lanes each job is run on. If necessary, one job could be run on two lanes, with a second job on the third lane. The "grouping" waste from a given set of jobs (let's say the quantities of them are x, y and z) would be the highest number minus the two lower numbers. So if x is the higher number, the grouping waste would be (x - y) + (x - z). Otherwise stated, waste is produced by printing job Y and Z (in excess of their quantities) up to the quantity of X. The grouping waste would be a qualifier for the given set, meaning it could not exceed a certain quantity or the job would simply be printed alone. So the question is stated: how to determine which sets of jobs are grouped together, out of any given number of jobs, based on the qualifiers of 1) Three similar quantities OR 2) Two quantities where one is approximately double the other, AND with the aim of minimal total grouping waste across the various sets. (Edit) Quantity Information: Typical job quantities can be from 150 to 350 on foreign languages, or 500 to 1000 on English print runs. This data can be used to set up some scenarios for an algorithm. For example, let's say you had 5 jobs: 1000, 500, 500, 450, 250 By looking at it, I can see a couple of answers. Obviously (1000/500/500) is not efficient as you'll have a grouping waste of 1000. (500/500/450) is better as you'll have a waste of 50, but then you run (1000) and (250) alone. But you could also run (1000/500) with 1000 on two lanes, (500/250) with 500 on two lanes and then (450) alone. In terms of trade-offs for lane minimization vs. wastage, we could say that any grouping waste over 200 is excessive. (End Edit) ...Needless to say, quite a problem. (For me.) I am a moderately skilled programmer but I do not have much familiarity with algorithms and I am not fully studied in the mathematics of the area. I'm I/P writing a sort of brute-force program that simply tries all options, neglecting any option tree that seems to have excessive grouping waste. However, I can't help but hope there's an easier and more efficient method. I've looked at various websites trying to find out more about algorithms in general and have been slogging my way through the symbology, but it's slow going. Unfortunately, Wikipedia's articles on the subject are very cross-dependent and it's difficult to find an "in". The only thing I've been able to really find would seem to be a definition of the rough type of algorithm I need: "Exclusive Distance Clustering", one-dimensionally speaking. I did look at what seems to be the popularly referred-to algorithm on this site, the Bin Packing one, but I was unable to see exactly how it would work with my problem. Any help is appreciated. :)

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• Order of parts in SMTP multipart messages

  - by Chris

  Hi, I'd like to know how to build an SMTP multipart message in the correct order so that it will render correctly on the iPhone mail client (rendering correctly in GMail). I'm using Javamail to build up an email containing the following parts: A body part with content type "text/html; UTF-8" An embedded image attachment. A file attachment I am sending the mail via GMail SMTP (via SSL) and the mail is sent and rendered correctly using a GMail account, however, the mail does not render correctly on the iPhone mail client. On the iPhone mail client, the image is rendered before the "Before Image" text when it should be rendered afterwards. After the "Before Image" text there is an icon with a question mark (I assume it means it couldn't find the referenced CID). I'm not sure if this is a limitation of the iPhone mail client or a bug in my mail sending code (I strongly assume the latter). I think that perhaps the headers on my parts might by incorrect or perhaps I am providing the multiparts in the wrong order. I include the text of the received mail as output by gmail (which renders the file correc Message-ID: <[email protected]> Subject: =?UTF-8?Q?Test_from_=E3=82=AF=E3=83=AA=E3=82=B9?= MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_0_20870565.1274154021755" ------=_Part_0_20870565.1274154021755 Content-Type: application/octet-stream Content-Transfer-Encoding: base64 Content-ID: <20100518124021763_368238_0> iVBORw0K ----- TRIMMED FOR CONCISENESS 6p1VVy4alAAAAABJRU5ErkJggg== ------=_Part_0_20870565.1274154021755 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit <html><head><title>Employees Favourite Foods</title> <style> body { font: normal 8pt arial; } th { font: bold 8pt arial; white-space: nowrap; } td { font: normal 8pt arial; white-space: nowrap; } </style></head><body> Before Image<br><img src="cid:20100518124021763_368238_0"> After Image<br><table border="0"> <tr> <th colspan="4">Employees Favourite Foods</th> </tr> <tr> <th align="left">Name</th><th align="left">Age</th><th align="left">Tel.No</th><th align="left">Fav.Food</th> </tr> <tr style="background-color:#e0e0e0"> <td>Chris</td><td>34</td><td>555-123-4567</td><td>Pancakes</td> </tr> </table></body></html> ------=_Part_0_20870565.1274154021755 Content-Type: text/plain; charset=us-ascii; name=textfile.txt Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=textfile.txt This is a textfile with numbers counting from one to ten beneath this line: one two three four five six seven eight nine ten(no trailing carriage return) ------=_Part_0_20870565.1274154021755-- Even if you can't assist me with this, I would appreciate it if any members of the forum could forward me a (non-personal) mail that includes inline images (not external hyperlinked images though). I just need to find a working sample then I can move past this. Thanks, Chris.

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• Dynamic model choice field in django formset using multiple select elements

  - by Aryeh Leib Taurog

  I posted this question on the django-users list, but haven't had a reply there yet. I have models that look something like this: class ProductGroup(models.Model): name = models.CharField(max_length=10, primary_key=True) def __unicode__(self): return self.name class ProductRun(models.Model): date = models.DateField(primary_key=True) def __unicode__(self): return self.date.isoformat() class CatalogItem(models.Model): cid = models.CharField(max_length=25, primary_key=True) group = models.ForeignKey(ProductGroup) run = models.ForeignKey(ProductRun) pnumber = models.IntegerField() def __unicode__(self): return self.cid class Meta: unique_together = ('group', 'run', 'pnumber') class Transaction(models.Model): timestamp = models.DateTimeField() user = models.ForeignKey(User) item = models.ForeignKey(CatalogItem) quantity = models.IntegerField() price = models.FloatField() Let's say there are about 10 ProductGroups and 10-20 relevant ProductRuns at any given time. Each group has 20-200 distinct product numbers (pnumber), so there are at least a few thousand CatalogItems. I am working on formsets for the Transaction model. Instead of a single select menu with the several thousand CatalogItems for the ForeignKey field, I want to substitute three drop-down menus, for group, run, and pnumber, which uniquely identify the CatalogItem. I'd also like to limit the choices in the second two drop-downs to those runs and pnumbers which are available for the currently selected product group (I can update them via AJAX if the user changes the product group, but it's important that the initial page load as described without relying on AJAX). What's the best way to do this? As a point of departure, here's what I've tried/considered so far: My first approach was to exclude the item foreign key field from the form, add the substitute dropdowns by overriding the add_fields method of the formset, and then extract the data and populate the fields manually on the model instances before saving them. It's straightforward and pretty simple, but it's not very reusable and I don't think it is the right way to do this. My second approach was to create a new field which inherits both MultiValueField and ModelChoiceField, and a corresponding MultiWidget subclass. This seems like the right approach. As Malcolm Tredinnick put it in a django-users discussion, "the 'smarts' of a field lie in the Field class." The problem I'm having is when/where to fetch the lists of choices from the db. The code I have now does it in the Field's __init__, but that means I have to know which ProductGroup I'm dealing with before I can even define the Form class, since I have to instantiate the Field when I define the form. So I have a factory function which I call at the last minute from my view--after I know what CatalogItems I have and which product group they're in--to create form/formset classes and instantiate them. It works, but I wonder if there's a better way. After all, the field should be able to determine the correct choices much later on, once it knows its current value. Another problem is that my implementation limits the entire formset to transactions relating to (CatalogItems from) a single ProductGroup. A third possibility I'm entertaining is to put it all in the Widget class. Once I have the related model instance, or the cid, or whatever the widget is given, I can get the ProductGroup and construct the drop-downs. This would solve the issues with my second approach, but doesn't seem like the right approach.

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• Have suggestions for these assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Are their any suggestions for this new assembly language?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• How can I implement the Gale-Shapley stable marriage algorithm in Perl?

  - by srk

  Problem : We have equal number of men and women.each men has a preference score toward each woman. So do the woman for each man. each of the men and women have certain interests. Based on the interest we calculate the preference scores. So initially we have an input in a file having x columns. First column is the person(men/woman) id. id are nothing but 0.. n numbers.(first half are men and next half woman) the remaining x-1 columns will have the interests. these are integers too. now using this n by x-1 matrix... we have come up with a n by n/2 matrix. the new matrix has all men and woman as their rows and scores for opposite sex in columns. We have to sort the scores in descending order, also we need to know the id of person related to the scores after sorting. So here i wanted to use hash table. once we get the scores we need to make up pairs.. for which we need to follow some rules. My trouble is with the second matrix of n by n/2 that needs to give information of which man/woman has how much preference on a woman/man. I need these scores sorted so that i know who is the first preferred woman/man, 2nd preferred and so on for a man/woman. I hope to get good suggestions on the data structures i use.. I prefer php or perl. Thank you in advance Hey guys this is not an home work. This a little modified version of stable marriage algorithm. I have working solution. I am only working on optimizing my code. more info: It is very similar to stable marriage problem but here we need to calculate the scores based on the interests they share. So i have implemented it as the way you see in the wiki page http://en.wikipedia.org/wiki/Stable_marriage_problem. my problem is not solving the problem. i solved it and can run it. I am just trying to have a better solution. so i am asking suggestions on the type of data structure to use. Conceptually I tried using an array of hashes. where the array index give the person id and the hash in it gives the id's <= score's in sorted manner. I initially start with an array of hashes. now i sort the hashes on values, but i could not store the sorted hashes back in an array.So just stored the keys after sorting and used these to get the values from my initial unsorted hashes. Can we store the hashes after sorting ? Can you suggest a better structure ?

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• Round-twice error in .NET's Double.ToString method

  - by Jeppe Stig Nielsen

  Mathematically, consider for this question the rational number 8725724278030350 / 2**48 where ** in the denominator denotes exponentiation, i.e. the denominator is 2 to the 48th power. (The fraction is not in lowest terms, reducible by 2.) This number is exactly representable as a System.Double. Its decimal expansion is 31.0000000000000'49'73799150320701301097869873046875 (exact) where the apostrophes do not represent missing digits but merely mark the boudaries where rounding to 15 resp. 17 digits is to be performed. Note the following: If this number is rounded to 15 digits, the result will be 31 (followed by thirteen 0s) because the next digits (49...) begin with a 4 (meaning round down). But if the number is first rounded to 17 digits and then rounded to 15 digits, the result could be 31.0000000000001. This is because the first rounding rounds up by increasing the 49... digits to 50 (terminates) (next digits were 73...), and the second rounding might then round up again (when the midpoint-rounding rule says "round away from zero"). (There are many more numbers with the above characteristics, of course.) Now, it turns out that .NET's standard string representation of this number is "31.0000000000001". The question: Isn't this a bug? By standard string representation we mean the String produced by the parameterles Double.ToString() instance method which is of course identical to what is produced by ToString("G"). An interesting thing to note is that if you cast the above number to System.Decimal then you get a decimal that is 31 exactly! See this Stack Overflow question for a discussion of the surprising fact that casting a Double to Decimal involves first rounding to 15 digits. This means that casting to Decimal makes a correct round to 15 digits, whereas calling ToSting() makes an incorrect one. To sum up, we have a floating-point number that, when output to the user, is 31.0000000000001, but when converted to Decimal (where 29 digits are available), becomes 31 exactly. This is unfortunate. Here's some C# code for you to verify the problem: static void Main() { const double evil = 31.0000000000000497; string exactString = DoubleConverter.ToExactString(evil); // Jon Skeet, http://csharpindepth.com/Articles/General/FloatingPoint.aspx Console.WriteLine("Exact value (Jon Skeet): {0}", exactString); // writes 31.00000000000004973799150320701301097869873046875 Console.WriteLine("General format (G): {0}", evil); // writes 31.0000000000001 Console.WriteLine("Round-trip format (R): {0:R}", evil); // writes 31.00000000000005 Console.WriteLine(); Console.WriteLine("Binary repr.: {0}", String.Join(", ", BitConverter.GetBytes(evil).Select(b => "0x" + b.ToString("X2")))); Console.WriteLine(); decimal converted = (decimal)evil; Console.WriteLine("Decimal version: {0}", converted); // writes 31 decimal preciseDecimal = decimal.Parse(exactString, CultureInfo.InvariantCulture); Console.WriteLine("Better decimal: {0}", preciseDecimal); // writes 31.000000000000049737991503207 } The above code uses Skeet's ToExactString method. If you don't want to use his stuff (can be found through the URL), just delete the code lines above dependent on exactString. You can still see how the Double in question (evil) is rounded and cast.

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• Asp.net with RegularExpression problem

  - by Eyla

  Greetings, I'm try to do valdation textbox input to valdate a phone number. I have a asp.net textbox and checkbox. the defualt is to validate a us phone number and when I check the checkbox I should change the RegularExpression and error message to validate an international phone using my own RegularExpression. I have no problem to validate the international phone but the problem is when validating the usa phone number I'm always getting error message that it is invalde phone number. I used diffrent RegularExpression but did not work. Please look at my code and davice me. Regards, ! ..................... ASP.net Code ..................... <%@ Page Language="C#" MasterPageFile="~/Master.Master" AutoEventWireup="true" CodeBehind="UpdateContact.aspx.cs" Inherits="IMAM_APPLICATION.UpdateContact" Title="Untitled Page" %> <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %> <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> <script src="js/jquery-1.4.1-vsdoc.js" type="text/javascript"></script> <script src="js/jquery.validate.js" type="text/javascript"></script> <script src="js/js.js" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function() { ValidPhoneHome("#<%= chkIntphoneHome%>"); $("#aspnetForm").validate({ // debug: true, rules: { "<%=txtHomePhone.UniqueID %>": { phonehome: true } }, errorElement: "mydiv", wrapper: "mydiv", // a wrapper around the error message errorPlacement: function(error, element) { offset = element.offset(); error.insertBefore(element) error.addClass('message'); // add a class to the wrapper error.css('position', 'absolute'); error.css('left', offset.left + element.outerWidth()); error.css('top', offset.top - (element.height() / 2)); } }); }) </script> <div id="mydiv"> <asp:CheckBox ID="chkIntphoneHome" runat="server" Text="Internation Code" Style="position: absolute; top: 620px; left: 700px;" onclick=" ValidPhoneHome(this)" /> <asp:TextBox ID="txtHomePhone" runat="server" Style="top: 650px; left: 700px; position: absolute; height: 22px; width: 128px" ></asp:TextBox> </div> </asp:Content> ............................. js.js File ................... var RegularExpression; var USAPhone = /(^[a-z]([a-z_\.]*)@([a-z_\.]*)([.][a-z]{3})$)|(^[a-z]([a-z_\.]*)@([a-z_\.]*)(\.[a-z]{3})(\.[a-z]{2})*$)/i; var InterPhone = /^\d{9,12}$/; var errmsg; function ValidPhoneHome(sender) { if (sender.checked == true) { RegularExpression = InterPhone; errmsg = "Enter 9 to 12 numbers as international number"; } else { RegularExpression = USAPhone; errmsg = "Enter a valid number"; } jQuery.validator.addMethod("phonehome", function(value, element) { return this.optional(element) || RegularExpression.test(value); }, errmsg); }

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• Are there any suggestions for these new assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Code golf: Word frequency chart

  - by ChristopheD

  The challenge: Build an ASCII chart of the most commonly used words in a given text. The rules: Only accept a-z and A-Z (alphabetic characters) as part of a word. Ignore casing (She == she for our purpose). Ignore the following words (quite arbitary, I know): the, and, of, to, a, i, it, in, or, is Clarification: considering don't: this would be taken as 2 different 'words' in the ranges a-z and A-Z: (don and t). Optionally (it's too late to be formally changing the specifications now) you may choose to drop all single-letter 'words' (this could potentially make for a shortening of the ignore list too). Parse a given text (read a file specified via command line arguments or piped in; presume us-ascii) and build us a word frequency chart with the following characteristics: Display the chart (also see the example below) for the 22 most common words (ordered by descending frequency). The bar width represents the number of occurences (frequency) of the word (proportionally). Append one space and print the word. Make sure these bars (plus space-word-space) always fit: bar + [space] + word + [space] should be always <= 80 characters (make sure you account for possible differing bar and word lenghts: e.g.: the second most common word could be a lot longer then the first while not differing so much in frequency). Maximize bar width within these constraints and scale the bars appropriately (according to the frequencies they represent). An example: The text for the example can be found here (Alice's Adventures in Wonderland, by Lewis Carroll). This specific text would yield the following chart: _________________________________________________________________________ |_________________________________________________________________________| she |_______________________________________________________________| you |____________________________________________________________| said |____________________________________________________| alice |______________________________________________| was |__________________________________________| that |___________________________________| as |_______________________________| her |____________________________| with |____________________________| at |___________________________| s |___________________________| t |_________________________| on |_________________________| all |______________________| this |______________________| for |______________________| had |_____________________| but |____________________| be |____________________| not |___________________| they |__________________| so For your information: these are the frequencies the above chart is built upon: [('she', 553), ('you', 481), ('said', 462), ('alice', 403), ('was', 358), ('that ', 330), ('as', 274), ('her', 248), ('with', 227), ('at', 227), ('s', 219), ('t' , 218), ('on', 204), ('all', 200), ('this', 181), ('for', 179), ('had', 178), (' but', 175), ('be', 167), ('not', 166), ('they', 155), ('so', 152)] A second example (to check if you implemented the complete spec): Replace every occurence of you in the linked Alice in Wonderland file with superlongstringstring: ________________________________________________________________ |________________________________________________________________| she |_______________________________________________________| superlongstringstring |_____________________________________________________| said |______________________________________________| alice |________________________________________| was |_____________________________________| that |______________________________| as |___________________________| her |_________________________| with |_________________________| at |________________________| s |________________________| t |______________________| on |_____________________| all |___________________| this |___________________| for |___________________| had |__________________| but |_________________| be |_________________| not |________________| they |________________| so The winner: Shortest solution (by character count, per language). Have fun! Edit: Table summarizing the results so far (2012-02-15) (originally added by user Nas Banov): Language Relaxed Strict ========= ======= ====== GolfScript 130 143 Perl 185 Windows PowerShell 148 199 Mathematica 199 Ruby 185 205 Unix Toolchain 194 228 Python 183 243 Clojure 282 Scala 311 Haskell 333 Awk 336 R 298 Javascript 304 354 Groovy 321 Matlab 404 C# 422 Smalltalk 386 PHP 450 F# 452 TSQL 483 507 The numbers represent the length of the shortest solution in a specific language. "Strict" refers to a solution that implements the spec completely (draws |____| bars, closes the first bar on top with a ____ line, accounts for the possibility of long words with high frequency etc). "Relaxed" means some liberties were taken to shorten to solution. Only solutions shorter then 500 characters are included. The list of languages is sorted by the length of the 'strict' solution. 'Unix Toolchain' is used to signify various solutions that use traditional *nix shell plus a mix of tools (like grep, tr, sort, uniq, head, perl, awk).

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• finishing some functions in this code

  - by osabri

  i have problem to finish some functions in this code program lab4; var inFile : text; var pArray : array[1..10]of real; //array of 10 integer values containing patterns to search in a given set of numbers var rArray : array[1..10]of integer; //array containing result of pattern search, each index in rArray coresponds to number of occurences of //pattern from pArray in sArray. var sArray : array[1..100] of real; //array containing data read from file var accuracy : real; (****************************************************************************) function errMsg:integer; begin if ParamCount < 3 then begin writeln('Too few arguments'); writeln('Usage: ./lab4 lab4.txt <accuracy> <pattern_1> <pattern_2> <pattern_n>'); errMsg:=-1; end else if ParamCount > 12 then begin writeln('Too many arguments'); writeln('Maximum number of patterns is 10'); errMsg:=-1; end else begin assign(inFile,ParamStr(1)); {$I-} reset(inFile); if ioresult<>0 then begin writeln('Cannot open ',ParamStr(1)); errMsg:=-1; end else errMsg:=0; end; end; (****************************************************************************) procedure readPattern; var errPos,idx:integer; begin if errMsg=0 then begin for idx:=1 to ParamCount-2 do begin Val(ParamStr(idx+2),pArray[idx],errPos); writeln('pArray:',pArray[idx]:2:2); end; end; end; (****************************************************************************) procedure getAccuracy; //Function should get the accuracy as the first param (after the program name) begin (here where i stopped : (( ) end; (****************************************************************************) function readSet:integer; //Function returns number of elements read from file var idx,errPos:integer; var sChar: string; begin if errMsg=0 then begin idx:=1; repeat begin readln(inFile,sChar); VAL(sChar,sArray[idx],errPos); writeln('sArray:',sArray[idx]:2:2); idx:=idx+1; end until eof(inFile)=TRUE; end; readSet:=idx-1; end; (****************************************************************************) procedure searchPattern(sNumber:integer); //Function should search and count pattern(patterns) occurence in a given set what the best solution for this part?? (****************************************************************************) procedure dispResult; //Function should display the result of pattern(patterns) search begin (****************************************************************************) begin readPattern; getAccuracy; searchPattern(readSet); dispResult; end.

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• Detecting Acceleration in a car (iPhone Accelerometer)

  - by TheGazzardian

  Hello, I am working on an iPhone app where we are trying to calculate the acceleration of a moving car. Similar apps have accomplished this (Dynolicious), but the difference is that this app is designed to be used during general city driving, not on a drag strip. This leads us to one big concern that Dynolicious was luckily able to avoid: hills. Yes, hills. There are two important stages to this: calibration, and actual driving. Our initial run was simple and suffered the consequences. During the calibration stage, I took the average force on the phone, and during running, I just subtracted the average force from the current force to get the current acceleration this frame. The problem with this is that the typical car receives much more force than just the forward force - everything from turning to potholes was causing the values to go out of sync with what was really happening. The next run was to add the condition that the iPhone must be oriented in such a way that the screen was facing toward the back of the car. Using this method, I attempted to follow only force on the z-axis, but this obviously lead to problems unless the iPhone was oriented directly upright, because of gravity. Some trigonometry later, and I had managed to work gravity out of the equation, so that the car was actually being read very, very well by the iPhone. Until I hit a slope. As soon as the angle of the car changed, suddenly I was receiving accelerations and decelerations that didn't make sense, and we were once again going out of sync. Talking with someone a lot smarter than me at math lead to a solution that I have been trying to implement for longer than I would like to admit. It's steps are as follows: 1) During calibration, measure gravity as a vector instead of a size. Store that vector. 2) When the car initially moves forward, take the vector of motion and subtract gravity. Use this as the forward momentum. (Ignore, for now, the user cases where this will be difficult and let's concentrate on the math :) 3) From the forward vector and the gravity vector, construct a plane. 4) Whenever a force is received, project it onto said plane to get rid of sideways force/etc. 5) Then, use that force, the known magnitude of gravity, and the known direction of forward motion to essentially solve a triangle to get the forward vector. The problem that is causing the most difficulty in this new system is not step 5, which I have gotten to the point where all the numbers look as they should. The difficult part is actually the detection of the forward vector. I am selecting vectors whose magnitude exceeds gravity, and from there, averaging them and subtracting gravity. (I am doing some error checking to make sure that I am not using a force just because the iPhone accelerometer was off by a bit, which happens more frequently than I would like). But if I plot these vectors that I am using, they actually vary by an angle of about 20-30 degrees, which can lead to some strong inaccuracies. The end result is that the app is even more inaccurate now than before. So basically - all you math and iPhone brains out there - any glaring errors? Any potentially better solutions? Any experience that could be useful at all? Award: offering a bounty of $250 to the first answer that leads to a solution.

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• Use QuickCheck by generating primes

  - by Dan

  Background For fun, I'm trying to write a property for quick-check that can test the basic idea behind cryptography with RSA. Choose two distinct primes, p and q. Let N = p*q e is some number relatively prime to (p-1)(q-1) (in practice, e is usually 3 for fast encoding) d is the modular inverse of e modulo (p-1)(q-1) For all x such that 1 < x < N, it is always true that (x^e)^d = x modulo N In other words, x is the "message", raising it to the eth power mod N is the act of "encoding" the message, and raising the encoded message to the dth power mod N is the act of "decoding" it. (The property is also trivially true for x = 1, a case which is its own encryption) Code Here are the methods I have coded up so far: import Test.QuickCheck -- modular exponentiation modExp :: Integral a => a -> a -> a -> a modExp y z n = modExp' (y `mod` n) z `mod` n where modExp' y z | z == 0 = 1 | even z = modExp (y*y) (z `div` 2) n | odd z = (modExp (y*y) (z `div` 2) n) * y -- relatively prime rPrime :: Integral a => a -> a -> Bool rPrime a b = gcd a b == 1 -- multiplicative inverse (modular) mInverse :: Integral a => a -> a -> a mInverse 1 _ = 1 mInverse x y = (n * y + 1) `div` x where n = x - mInverse (y `mod` x) x -- just a quick way to test for primality n `divides` x = x `mod` n == 0 primes = 2:filter isPrime [3..] isPrime x = null . filter (`divides` x) $ takeWhile (\y -> y*y <= x) primes -- the property prop_rsa (p,q,x) = isPrime p && isPrime q && p /= q && x > 1 && x < n && rPrime e t ==> x == (x `powModN` e) `powModN` d where e = 3 n = p*q t = (p-1)*(q-1) d = mInverse e t a `powModN` b = modExp a b n (Thanks, google and random blog, for the implementation of modular multiplicative inverse) Question The problem should be obvious: there are way too many conditions on the property to make it at all usable. Trying to invoke quickCheck prop_rsa in ghci made my terminal hang. So I've poked around the QuickCheck manual a bit, and it says: Properties may take the form forAll <generator> $ \<pattern> -> <property> How do I make a <generator> for prime numbers? Or with the other constraints, so that quickCheck doesn't have to sift through a bunch of failed conditions? Any other general advice (especially regarding QuickCheck) is welcome.

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• Dynamically specify the type in C#

  - by Lirik

  I'm creating a custom DataSet and I'm under some constrains: I want the user to specify the type of the data which they want to store. I want to reduce type-casting because I think it will be VERY expensive. I will use the data VERY frequently in my application. I don't know what type of data will be stored in the DataSet, so my initial idea was to make it a List of objects, but I suspect that the frequent use of the data and the need to type-cast will be very expensive. The basic idea is this: class DataSet : IDataSet { private Dictionary<string, List<Object>> _data; /// <summary> /// Constructs the data set given the user-specified labels. /// </summary> /// <param name="labels"> /// The labels of each column in the data set. /// </param> public DataSet(List<string> labels) { _data = new Dictionary<string, List<object>>(); foreach (string label in labels) { _data.Add(label, new List<object>()); } } #region IDataSet Members public List<string> DataLabels { get { return _data.Keys.ToList(); } } public int Count { get { _data[_data.Keys[0]].Count; } } public List<object> GetValues(string label) { return _data[label]; } public object GetValue(string label, int index) { return _data[label][index]; } public void InsertValue(string label, object value) { _data[label].Insert(0, value); } public void AddValue(string label, object value) { _data[label].Add(value); } #endregion } A concrete example where the DataSet will be used is to store data obtained from a CSV file where the first column contains the labels. When the data is being loaded from the CSV file I'd like to specify the type rather than casting to object. The data could contain columns such as dates, numbers, strings, etc. Here is what it could look like: "Date","Song","Rating","AvgRating","User" "02/03/2010","Code Monkey",4.6,4.1,"joe" "05/27/2009","Code Monkey",1.2,4.5,"jill" The data will be used in a Machine Learning/Artificial Intelligence algorithm, so it is essential that I make the reading of data very fast. I want to eliminate type-casting as much as possible, since I can't afford to cast from 'object' to whatever data type is needed on every read. I've seen applications that allow the user to pick the specific data type for each item in the csv file, so I'm trying to make a similar solution where a different type can be specified for each column. I want to create a generic solution so I don't have to return a List<object> but a List<DateTime> (if it's a DateTime column) or List<double> (if it's a column of doubles). Is there any way that this can be achieved? Perhaps my approach is wrong, is there a better approach to this problem?

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• Why isn't this javascript with else if working?

  - by Uni

  I'm sorry I can't be any more specific - I have no idea where the problem is. I'm a total beginner, and I've added everything I know to add to the coding, but nothing happens when I push the button. I don't know at this point if it's an error in the coding, or a syntax error that makes it not work. Basically I am trying to get this function "Rip It" to go through the list of Dewey decimal numbers, change some of them, and return the new number and a message saying it's been changed. There is also one labeled "no number" that has to return an error (not necessarily an alert box, a message in the same space is okay.) I am a total beginner and not particularly good at this stuff, so please be gentle! Many thanks! <!DOCTYPE html> <html> <head> <script type="text/javascript"> function RipIt() { for (var i = l; i <=10 i=i+l) { var dewey=document.getElementById(i); dewey=parseFloat(dewey); if (dewey >= 100 && 200 >= dewey) { document.getElementById('dewey'+ 100) } else if (dewey >= 400 && 500 >= dewey) { document.getElementById('dewey'+ 200) } else if (dewey >= 850 && 900 >= dewey) { document.getElementById('dewey'-100) } else if (dewey >= 600 && 650 >= dewey) { document.getElementById('dewey'+17) } } } </script> </head> <body> <h4>Records to Change</h4> <ul id="myList"> <li id ="1">101.33</li> <li id = "2">600.01</li> <li id = "3">001.11</li> <li id = "4">050.02</li> <li id = "5">199.52</li> <li id = "6">400.27</li> <li id = "7">401.73</li> <li id = "8">404.98</li> <li id = "9">no number</li> <li id = "10">850.68</li> <li id = "11">853.88</li> <li id = "12">407.8</li> <li id = "13">878.22</li> <li id = "14">175.93</li> <li id = "15">175.9</li> <li id = "16">176.11</li> <li id = "17">190.97</li> <li id = "18">90.01</li> <li id = "19">191.001</li> <li id = "20">600.95</li> <li id = "21">602.81</li> <li id = "22">604.14</li> <li id = "23">701.31</li> <li id = "24">606.44</li> <li id = "25">141.77</li> </ul> <b> </b> <input type="button" value="Click To Run" onclick="RipIt()"> <!-- <input type="button" value="Click Here" onClick="showAlert();"> --> </body> </html>

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