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  • Programming languages with a Lisp-like syntax extension mechanism

    - by Giorgio
    I have only a limited knowledge of Lisp (trying to learn a bit in my free time) but as far as I understand Lisp macros allow to introduce new language constructs and syntax by describing them in Lisp itself. This means that a new construct can be added as a library, without changing the Lisp compiler / interpreter. This approach is very different from that of other programming languages. E.g., if I wanted to extend Pascal with a new kind of loop or some particular idiom I would have to extend the syntax and semantics of the language and then implement that new feature in the compiler. Are there other programming languages outside the Lisp family (i.e. apart from Common Lisp, Scheme, Clojure (?), Racket (?), etc) that offer a similar possibility to extend the language within the language itself? EDIT Please, avoid extended discussion and be specific in your answers. Instead of a long list of programming languages that can be extended in some way or another, I would like to understand from a conceptual point of view what is specific to Lisp macros as an extension mechanism, and which non-Lisp programming languages offer some concept that is close to them.

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  • Do you think that exposure to BASIC can mutilate your mind? [closed]

    - by bigown
    It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration -- Edsger W. Dijkstra I have deep respect to Dijkstra but I don't agree with everything he said/wrote. I disagree specially with this quote on linked paper wrote 35 years ago about the Dartmouth BASIC implementation. Many of my coworkers or friends programmers started with BASIC, questions below have answers that indicate many programmers had their first experience on programming at BASIC. AFAIK many good programmers started at BASIC programming. I'm not talking about Visual Basic or other "modern" dialects of BASIC running on machines full of resources. I'm talking about old times BASIC running on "toy" computer, that the programmer had to worry about saving small numbers that need not be calculated as a string to save a measly byte because the computer had only a few hundreds of them, or have to use computed goto for lack of a more powerful feature, and many other things which require the programmer to think much before doing something and forcing the programmer to be creative. If you had experience with old time BASIC on a machine with limited resources (have in mind that a simple micro-controller today has much more resources than a computer in 1975, do you think that BASIC help your mind to find better solutions, to think like an engineer or BASIC drag you to dark side of programming and mutilated you mentally? Is good to learn a programming language running on a computer full of resources where the novice programmer can do all wrong and the program runs without big problems? Or is it better to learn where the programmer can't go wrong? What can you say about the BASIC have helped you to be a better/worse programmer? Would you teach old BASIC running on a 2KB (virtual) machine to a coming programmer? Sure, only exposure to BASIC is bad. Maybe you share my opinion that modern BASIC doesn't help too much because modern BASIC, as long other programming languages, gives facilities which allow the programmer doesn't think deeper. Additional information: Why BASIC?

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  • Extending Programming Languages

    - by chpwn
    (Since I just posted this in another question, but my browser had to be annoying and submit it without content first, here it is again:) I'm a fan of clean code. I like my languages to be able to express what I'm trying to do, but I like the syntax to mirror that too. For example, I work on a lot of programs in Objective-C for jailbroken iPhones, which patch other code using the method_setImplementation() function of the runtime. Or, in pyobjc, I have to use the syntax UIView.initWithFrame_(), which is also pretty awful and unreadable with the way the method names are structured. In both cases, the language does not support this in syntax. I've found three basic ways that this is done: Insane macros. Take a look at this "CaptainHook", it does what I'm looking for in a usable way, but it isn't quite clean and is a major hack. There's also "Logos", which implements a very nice syntax, but is written in Perl parsing my code with a ton of regular expressions. This scares me. I like the idea of adding a %hook ClassName, but not by using regular expressions to parse C or Objective-C. Finally, there is Cycript. This is an extension to JavaScript which interfaces with the Objective-C runtime and allows you to use Objective-C style code in your JavaScript, and inject that into other processes. This is likely the cleanest as it actually uses a parser for the JavaScript, but I'm not a huge fan of that language in general. Basically, this is a two part question. Should, and how should, I create an extension to Python and Objective-C to allow me to do this? Is it worth writing a parser for my language to transform the syntax into something nicer, if it is only in a very specialized niche like this? Should I just live with the horrible syntax of the default Objective-C hooking or pyobjc?

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  • How to escape % in roxygen literate programming?

    - by Karsten W.
    The default value of a parameter of my function contains a "%". This seems to be a problem for roxygen, it produces a lot of warnings and R CMD check fails when trying to build latex documentation. How can I make this function (and its documentation) work? Using %% or \% instead of % does not help. #' Test escape \% from in-source documentation (roxygen). #' #' What happens when parameters contain special latex characters? #' #' @param x unsuspicious parameter #' @param format sprintf format string (default "\%5.0f") #' #' @return formatted string #' @export #' @author Karsten Weinert testroxy <- function(x, format = "%5.0f") { sprintf(format,x) }

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  • Please give the solution of the following programs in R Programming

    - by NEETHU
    Table below gives data concerning the performance of 28 national football league teams in 1976.It is suspected that the no. of yards gained rushing by opponents(x8) has an effect on the no. of games won by a team(y) (a)Fit a simple linear regression model relating games won by y to yards gained rushing by opponents x8. (b)Construct the analysis of variance table and test for significance of regression. (c)Find a 95% CI on the slope. (d)What percent of the total variability in y is explained by this model. (e)Find a 95% CI on the mean number of games won in opponents yards rushing is limited to 2000 yards. Team y x8 1 10 2205 2 11 2096 3 11 1847 4 13 1803 5 10 1457 6 11 1848 7 10 1564 8 11 1821 9 4 2577 10 2 2476 11 7 1984 12 10 1917 13 9 1761 14 9 1709 15 6 1901 16 5 2288 17 5 2072 18 5 2861 19 6 2411 20 4 2289 21 3 2203 22 3 2592 23 4 2053 24 10 1979 25 6 2048 26 8 1786 27 2 2876 28 0 2560 Suppose we would like to use the model developed in problem 1 to predict the no. of games a team will win if it can limit opponents yards rushing to 1800 yards. Find a point estimate of the no. of games won when x8=1800.Find a 905 prediction interval on the no. of games won. The purity of Oxygen produced by a fractionation process is thought to be percentage of Hydrocarbon in the main condenser of the processing unit .20 samples are shown below. Purity(%) Hydrocarbon(%) 86.91 1.02 89.85 1.11 90.28 1.43 86.34 1.11 92.58 1.01 87.33 0.95 86.29 1.11 91.86 0.87 95.61 1.43 89.86 1.02 96.73 1.46 99.42 1.55 98.66 1.55 96.07 1.55 93.65 1.4 87.31 1.15 95 1.01 96.85 0.99 85.2 0.95 90.56 0.98 (a)Fit a simple linear regression model to the data. (b)Test the hypothesis H0:ß=0 (c)Calculate R2 . (d)Find a 95% CI on the slope. (e)Find a 95% CI on the mean purity and the Hydrocarbon % is 1. Consider the Oxygen plant data in Problem3 and assume that purity and Hydrocarbon percentage are jointly normally distributed r.vs (a)What is the correlation between Oxygen purity and Hydrocarbon% (b)Test the hypothesis that ?=0. (c)Construct a 95% CI for ?.

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  • c# Network Programming - HTTPWebRequest Scraping

    - by masterguru
    Hi, I am building a web scraping application. It should scrape a complex web site with concurrent HttpWebRequests from a single host to a single target web server. The application should run on Windows server 2008. One single HttpWebRequest for data could take from 1 minute to 4 minutes to complete (because of long running db operations) I should have at least 100 parallel requests to the target web server, but i have noticed that when i use more then 2-3 long-running requests i have big performance issues (request timeouts/hanging). How many concurrent requests can i have in this scenario from a single host to a single target web server? can i use Thread Pools in the application to run parallel HttpWebRequests to the server? will i have any issues with the default outbound HTTP connection/requests limits? what about Request timeouts when i reach outbound connection limits? what would be the best setup for my scenario? Any help would be appreciated. Thanks

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  • Programming language shootout: code most like pseudocode for Dijkstra's Algorithm

    - by Casebash
    Okay, so this question here asked which language is most like executable pseudocode, so why not find out by actually writing some code! Here we have a competition where I will award a 100 point bounty (I know its not much, but I am poor after the recalc) to the code which most resembles this pseudocode. I've read through this a few times so I'm pretty sure that this pseudocode below is correct and about as unambiguous as pseudocode can be. Personally, I'm going to have a go in Python and probably Haskell as well, but I'm just learning the later so my attempt will probably be pretty poor. Note: Obviously to implement anything looking like this you'll have to define quite a few library functions. define DirectedGraph G with: Vertices as V, Edges as E define Vertex A, Z declare each e in E as having properties: Boolean fixed with: initial=false Real minSoFar with: initial=0 for A else infinity define PriorityQueue pq with: objects=V initial=A priority v=v.minSoFar create triggers for v in V: when v.minSoFar event reduced then pq.addOrUpdate v when v.fixed event becomesTrue then pq.remove v Repeat until Z.fixed==True: define Vertex U=pq.pop() U.fixed=True for Edge E adjacentTo U with other Vertex V: V.minSoFar=U.minSoFar+length(E) if reducesValue return Z.name, Z.minSoFar

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  • C#.NET Socket Programming: Connecting to remote computers.

    - by Gio Borje
    I have a typical server in my end and a friend using a client to connect to my IP/Port and he consistently receives the exception: "A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond {MY_IP}:{MY_PORT}"—You don't need to know my IP. The client and server, however, work fine on the loopback address (127.0.0.1). I also do not have any firewall nor is windows firewall active. Server: static void Main(string[] args) { Console.Title = "Socket Server"; Console.WriteLine("Listening for messages..."); Socket serverSock = new Socket( AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPAddress serverIP = IPAddress.Any; IPEndPoint serverEP = new IPEndPoint(serverIP, 33367); SocketPermission perm = new SocketPermission(NetworkAccess.Accept, TransportType.Tcp, "98.112.235.18", 33367); serverSock.Bind(serverEP); serverSock.Listen(10); while (true) { Socket connection = serverSock.Accept(); Byte[] serverBuffer = new Byte[8]; String message = String.Empty; while (connection.Available > 0) { int bytes = connection.Receive( serverBuffer, serverBuffer.Length, 0); message += Encoding.UTF8.GetString( serverBuffer, 0, bytes); } Console.WriteLine(message); connection.Close(); } } Client: static void Main(string[] args) { // Design the client a bit Console.Title = "Socket Client"; Console.Write("Enter the IP of the server: "); IPAddress clientIP = IPAddress.Parse(Console.ReadLine()); String message = String.Empty; while (true) { Console.Write("Enter the message to send: "); // The messsage to send message = Console.ReadLine(); IPEndPoint clientEP = new IPEndPoint(clientIP, 33367); // Setup the socket Socket clientSock = new Socket( AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // Attempt to establish a connection to the server Console.Write("Establishing connection to the server... "); try { clientSock.Connect(clientEP); // Send the message clientSock.Send(Encoding.UTF8.GetBytes(message)); clientSock.Shutdown(SocketShutdown.Both); clientSock.Close(); Console.Write("Message sent successfully.\n\n"); } catch (Exception ex) { Console.WriteLine(ex.Message); } } }

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  • Are there some general Network programming best practices?

    - by uriDium
    I am implementing some networking stuff in our project. It has been decided that the communication is very important and we want to do it synchronously. So the client sends something the server acknowledges. Are there some general best practices for the interaction between the client and the server. For instance if there isn't an answer from the server should the client automatically retry? Should there be a timeout period before it retries? What happens if the acknowledgement fails? At what point do we break the connection and reconnect? Is there some material? I have done searches but nothing is really coming up. I am looking for best practices in general. I am implementing this in c# (probably with sockets) so if there is anything .Net specific then please let me know too.

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  • Ruby Programming Techniques: simple yet not so simple object manipulation

    - by Shyam
    Hi, I want to create an object, let's say a Pie. class Pie def initialize(name, flavor) @name = name @flavor = flavor end end But a Pie can be divided in 8 pieces, a half or just a whole Pie. For the sake of argument, I would like to know how I could give each Pie object a price per 1/8, 1/4 or per whole. I could do this by doing: class Pie def initialize(name, flavor, price_all, price_half, price_piece) @name = name @flavor = flavor @price_all = price_all @price_half = price_half @price_piece = price_piece end end But now, if I would create fifteen Pie objects, and I would take out randomly some pieces somewhere by using a method such as getPieceOfPie(pie_name) How would I be able to generate the value of all the available pies that are whole and the remaining pieces? Eventually using a method such as: myCurrentInventoryHas(pie_name) # output: 2 whole strawberry pies and 7 pieces. I know, I am a Ruby nuby. Thank you for your answers, comments and help!

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  • Need help with dynamic programming problem

    - by John Retallack
    I have the following problem : I am given a tree with N apples, for each apple I am given it's weight and height,I can pick apples up to a given height H,each time I pick an apple the height of every apple is increased with U(also given).I have to find out the maximum weight of apples I can pick. e.g: N=4 H=100 U=10 (height-eight) apple1: 91 10 apple2: 82 30 apple3: 93 5 apple4: 94 15 The answer is 45 : I first pick the apple with the weight of 15 then the one with the weight of 30. I would like to know if someone here could help me with giving me an hint on how I should approach this problem. Thank you.

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  • programming logic and design pleas friends i need a flowcharts or pseudocode

    - by alex
    ***the midvile park maintains records containing info about players on it's soccer teams . each record contain a players first name,last name,and team number . the team are team number team name 1 goal getters 2 the force 3 top gun 4 shooting stars 5 midfield monsters design a proggram that accept player data and creates a report that lists each** player a long with his or her team number and team name**

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  • Archery game programming algorithm

    - by Ricky
    I need the algorithm to animate the arrow based on 2 parameters, angle while shooting and power while drawing the bow. Ive tried to use y=asinx but it works only when shooting in up direction. Doesnt work well while shooting with straight or down direction. Thanks.

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  • DRY programming dilemma

    - by fayer
    the situation is like this: im creating a Logger class that can write to a file but the write_to_file() function is in a helper class as a static function. i could call that function but then the Log class would be dependent to the helper class. isn't dependency bad? but if i can let it use a helper function then what is the point of having helper functions? what should one prioritize here: using helper functions and have to include this helper class everywhere (but the other 99 methods wont be useful) or just copy and paste into the Log class (but then if i have done this 100 times and then make a change i have to change in 100 places). share your thoughts and experience!

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  • Initial Genetic Programming Parameters

    - by cmptrer
    I did a little GP (note:very little) work in college and have been playing around with it recently. My question is in regards to the intial run settings (population size, number of generations, min/max depth of trees, min/max depth of initial trees, percentages to use for different reproduction operations, etc.). What is the normal practice for setting these parameters? What papers/sites do people use as a good guide?

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  • Gotchas In Programming Languages.

    - by Draco Ater
    There is a collection of "very special irregularities, inconstancies and just plain painfully unintuitive moments" concerning javascript on wtfjs. Do you know some other collections of such unintuitive moments for other languages?

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  • Genetic Programming Online Learning

    - by Lirik
    Has anybody seen a GP implemented with online learning rather than the standard offline learning? I've done some stuff with genetic programs and I simply can't figure out what would be a good way to make the learning process online. Please let me know if you have any ideas, seen any implementations, or have any references that I can look at.

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  • Practical Scheme Programming

    - by Ixmatus
    It's been a few months since I've touched Scheme and decided to implement a command line income partitioner using Scheme. My initial implementation used plain recursion over the continuation, but I figured a continuation would be more appropriate to this type of program. I would appreciate it if anyone (more skilled with Scheme than I) could take a look at this and suggest improvements. I'm that the multiple (display... lines is an ideal opportunity to use a macro as well (I just haven't gotten to macros yet). (define (ab-income) (call/cc (lambda (cc) (let ((out (display "Income: ")) (income (string->number (read-line)))) (cond ((<= income 600) (display (format "Please enter an amount greater than $600.00~n~n")) (cc (ab-income))) (else (let ((bills (* (/ 30 100) income)) (taxes (* (/ 20 100) income)) (savings (* (/ 10 100) income)) (checking (* (/ 40 100) income))) (display (format "~nDeduct for bills:---------------------- $~a~n" (real->decimal-string bills 2))) (display (format "Deduct for taxes:---------------------- $~a~n" (real->decimal-string taxes 2))) (display (format "Deduct for savings:-------------------- $~a~n" (real->decimal-string savings 2))) (display (format "Remainder for checking:---------------- $~a~n" (real->decimal-string checking 2)))))))))) Invoking (ab-income) asks for input and if anything below 600 is provided it (from my understanding) returns (ab-income) at the current-continuation. My first implementation (as I said earlier) used plain-jane recursion. It wasn't bad at all either but I figured every return call to (ab-income) if the value was below 600 kept expanding the function. (please correct me if that apprehension is incorrect!)

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  • C Programming - My program is good enough for my assignment but I know its not good

    - by Joe
    Hi there I'm just starting an assignment for uni and it's raised a question for me. I don't understand how to return a string from a function without having a memory leak. char* trim(char* line) { int start = 0; int end = strlen(line) - 1; /* find the start position of the string */ while(isspace(line[start]) != 0) { start++; } //printf("start is %d\n", start); /* find the position end of the string */ while(isspace(line[end]) != 0) { end--; } //printf("end is %d\n", end); /* calculate string length and add 1 for the sentinel */ int len = end - start + 2; /* initialise char array to len and read in characters */ int i; char* trimmed = calloc(sizeof(char), len); for(i = 0; i < (len - 1); i++) { trimmed[i] = line[start + i]; } trimmed[len - 1] = '\0'; return trimmed; } as you can see I am returning a pointer to char which is an array. I found that if I tried to make the 'trimmed' array by something like: char trimmed[len]; then the compiler would throw up a message saying that a constant was expected on this line. I assume this meant that for some reason you can't use variables as the array length when initialising an array, although something tells me that can't be right. So instead I made my array by allocating some memory to a char pointer. I understand that this function is probably waaaaay sub-optimal for what it is trying to do, but what I really want to know is: 1. Can you normally initialise an array using a variable to declare the length like: char trimmed[len]; ? 2. If I had an array that was of that type (char trimmed[]) would it have the same return type as a pointer to char (ie char*). 3. If I make my array by callocing some memory and allocating it to a char pointer, how do I free this memory. It seems to me that once I have returned this array, I can't access it to free it as it is a local variable. Many thanks in advance Joe

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  • Which Programming Language Should I Learn?

    - by Esteban Araya
    I've decided, for educational purposes, I want to learn a new language every 2 years or so. Which language should I learn first? Why? I'm proficient with C, C# and Java. Other than that, I really haven't done much with any other languages. Thanks! Edit: Thanks to all of those that recommended functional languages. Making the mental switch to a functional language seems hard. How did you overcome your instinct to keep doing things in a procedural manner?

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  • Can you do Logic Programming in Scala?

    - by Alex R
    I read somewhere that Pattern Matching like that supported by the match/case feature in Scala was actually borrowed from Logic languages like Prolog. Can you use Scala to elegantly solve problems like the Connected Graph problem? e.g. https://www.csupomona.edu/~jrfisher/www/prolog_tutorial/2_15.html

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