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  • Help me sort programing languages a bit

    - by b-gen-jack-o-neill
    Hi, so I asked here few days ago about C# and its principles. Now, if I may, I have some additional general questions about some languages, becouse for novice like me, it seems a bit confusing. To be exact I want to ask more about language functions capabilities than syntax and so. To be honest, its just these special functions that bothers me and make me so confused. For exmaple, C has its printf(), Pascal has writeln() and so. I know in basic the output in assembler of these funtions would be similiar, every language has more or less its special functions. For console output, for file manipulation, etc. But all these functions are de-facto part of its OS API, so why is for example in C distinguished between C standard library functions and (on Windows) WinAPI functions when even printf() has to use some Windows feature, call some of its function to actually show desired text on console window, becouse the actuall "showing" is done by OS. Where is the line between language functions and system API? Now languages I dont quite understand - Python, Ruby and similiar. To be more specific, I know they are similiar to java and C# in term they are compiled into bytecode. But, I do not unerstand what are its capabilities in term of building GUI applications. I saw tutorial for using Ruby to program GUI applications on Linux and Windows. But isn´t that just some kind of upgrade? I mean fram other tutorials It seemed like these languages was first intended for small scripts than building big applications. I hope you understand why I am confused. If you do, please help me sort it out a bit, I have no one to ask.

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  • Haskell: Why is it saying my function type is off?

    - by linkmaster03
    I wrote a little Haskell program to find the area of a triangle, primarily to practice custom types, but it keeps throwing the following error on compile: areafinder.hs:7:4: Couldn't match expected type 'Triangle' against inferred type 'm b' In a stmt of a 'do' expression: putStr "Base: " In the expression: do { putStr "Base: "; baseStr I'm not sure where 'm b' comes from, so I'm at a loss here. Why is it throwing this error, and what can I do to fix it? Here is my code: module Main where data Triangle = Triangle Double Double -- base, height getTriangle :: Triangle getTriangle = do putStr "Base: " baseStr Double calcTriangle (Triangle base height) = base * height main = putStrLn ("Area = " ++ show (calcTriangle getTriangle)) Thanks. :)

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  • Help Me Make My Pascal Program Display Multiple Names Which Were Entered Plz.

    - by Sketchie
    Hey,Guys I'm having trouble displaying names using arrays in my Pascal program. But first heres the question I'm writing the program to answer : Develop pseudocode that accepts as input the name of an unspecified number of masqueraders who each have paid the full cost of their costume and the amount each has paid. A masquerader may have paid for a costume in any of the five sections in the band. The algorithm should determine the section in which the masquerader plays, based on the amount he/she has paid for the costume. The algorithm should also determine the number of masqueraders who have paid for costumes in each section. The names of persons and the section for which they have paid should be printed. A listing of the sections and the total number of persons registered to play in each section should also be printed, along with the total amount paid in each section. And here's what I've done so far(It's a bit messy): program Maqueprgrm; uses wincrt; type names=array [1..30]of string; var name:string; s1_nms:names; s2_nms:names; s3_nms:names; s4_nms:names; s5_nms:names; amt_paid:integer; stop,x,full,ins,ttl1,ttl2,ttl3,ttl4,ttl5,sec_1,sec_2,sec_3,sec_4,sec_5,sec:integer; begin stop := 0; writeln ('To Begin Data Collecting Section Press 1, To End Press 0'); readln(stop); while stop <0 do begin for x:= 1 to 30 do x:= x+1; writeln ('Please Enter The Name of Masquerader.'); readln (name); writeln ('Please Enter The Amount Paid For Costume.'); readln (amt_paid); IF amt_paid = 144 THEN Begin full:=full+1; {people who paid in full + 1} sec_1:=sec_1+1; {people in this section + 1} ttl1:= ttl1+amt_paid; {total money earned in this section + amount person paid} s1_nms[x]:= name; {People's names in this section plus current entry's name} End else IF amt_paid = 184 then Begin ins:=ins+1; sec_1:=sec_1+1; ttl1:=ttl1+amt_paid; s1_nms[x]:= name; end else IF amt_paid = 198 then Begin full:=full+1; sec_2:=sec_2+1; ttl2:=ttl2+amt_paid; s2_nms[x]:= 'name'; end else IF amt_paid = 153 then Begin ins:=ins+1; sec_2:=sec_2+1; ttl2:=ttl2+amt_paid; s2_nms[x]:= 'name'; end else IF amt_paid = 264 then Begin full:=full+1; sec_3:=sec_3+1; ttl3:=ttl3+amt_paid; s3_nms[x]:= 'name'; end else IF amt_paid = 322 then Begin ins:=ins+1; sec_3:=sec_3+1; ttl3:=ttl3+amt_paid; s3_nms[x]:= 'name'; end else IF amt_paid = 315 then Begin full:=full+1; sec_4:=sec_4+1; ttl4:=ttl4+amt_paid; s4_nms[x]:= 'name'; end else IF amt_paid = 402 then Begin ins:=ins+1; sec_4:=sec_4+1; ttl4:=ttl4+amt_paid; s4_nms[x]:= 'name'; end else IF amt_paid = 382. then Begin ins:=ins+1; sec_4:=sec_4+1; ttl4:=ttl4+amt_paid; s4_nms[x]:= 'name'; end else IF amt_paid = 488 then Begin ins:=ins+1; sec_5:=sec_5+1; ttl5:=ttl5+amt_paid; s5_nms[x]:= 'name'; end else begin Writeln ('Invalid Entry'); For x:= 1 to 30 do end; writeln (' To Enter More Data Press 1, To Print Data and Calculations Press 0'); Readln (stop); End; writeln ('For Information on Sections Press 1, 2, 3, 4, or 5 Respectively'); Readln (sec); IF Sec= 1 THEN Begin for x:= 1 to 30 do; begin writeln ('The Number of Revelers in This Section is ',Sec_1,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Full Is ', Full,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Installments is ', Ins ,'.'); Writeln ('The Names of Revelers in This Section is ', S1_Nms[x], '.'); Writeln ('The Total Amount Collected By This Section Is ', Ttl1, '.'); End; end else IF Sec= 2 THEN Begin For x:= 1 to 30 do begin Writeln ('The Number of Revelers in This Section is ', Sec_2,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Full Is ', Full,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Installments is ', Ins ,'.'); Writeln ('The Names of Revelers in This Section is ', S2_Nms[x] ,'.'); Writeln ('The Total Amount Collected By This Section Is ', Ttl2, '.'); End; End else IF Sec= 3 THEN Begin For x:= 1 to 30 do begin writeln ('The Number of Revelers in This Section is ', Sec_3,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Full Is ', Full,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Installments is ', Ins ,'.'); Writeln ('The Names of Revelers in This Section is ', S3_Nms[x] ,'.'); Writeln ('The Total Amount Collected By This Section Is ', Ttl3, '.'); End; End else IF Sec= 4 THEN Begin For x:= 1 to 30 do begin writeln ('The Number of Revelers in This Section is ', Sec_4,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Full Is ', Full,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Installments is ', Ins, '.'); Writeln ('The Names of Revelers in This Section is ', S4_Nms [x],'.'); Writeln ('The Total Amount Collected By This Section Is ', Ttl4 ,'.'); End; End else IF Sec= 5 THEN Begin For x:= 1 to 30 do begin writeln ('The Number of Revelers in This Section is ', Sec_5,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Full Is ', Full,'.'); Writeln ('The Number of Revelers in the Band Who Paid in Installments is ', Ins, '.'); Writeln ('The Names of Revelers in This Section is ', S5_Nms[x], '.'); Writeln ('The Total Amount Collected By This Section Is ', Ttl5 ,'.'); End; End else BEGIN Writeln ('Invalid Entry. For Information on Sections Press 1, 2, 3, 4, or 5 Respectively. '); End; end. The result I keep getting is that for the names in the section it is only the name of the last person entered that is displayed. For example it would display: The number of revelers in this section is 2 The number of revelers in the band who paid in full is 2 {Band is the whole thing divided into 5 section} The number of revelers in the band who paid in installments is 0 The names of revelers in this section is Amy Total amount collected by this section is 288 So yea, the program only displays "Amy" even though I entered more than 1 name. Do you guys know how to fix it also if it's not asking too much could you help me to make a while loop for the last portion of the program so that after the user sees the info for a section he can see another section. It sucks that I've been working on it for a while but if it doesn't run properly tomorrow I'll fail. Help would be greatly appreciated and responses are welcome anytime cause i'll be up anyway. P.S. Sorry for the long post.

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  • Permuting output of a tree of closures

    - by yan
    This a conceptual question on how one would implement the following in Lisp (assuming Common Lisp in my case, but any dialect would work). Assume you have a function that creates closures that sequentially iterate over an arbitrary collection (or otherwise return different values) of data and returns nil when exhausted, i.e. (defun make-counter (up-to) (let ((cnt 0)) (lambda () (if (< cnt up-to) (incf cnt) nil)))) CL-USER> (defvar gen (make-counter 3)) GEN CL-USER> (funcall gen) 1 CL-USER> (funcall gen) 2 CL-USER> (funcall gen) 3 CL-USER> (funcall gen) NIL CL-USER> (funcall gen) NIL Now, assume you are trying to permute a combinations of one or more of these closures. How would you implement a function that returns a new closure that subsequently creates a permutation of all closures contained within it? i.e.: (defun permute-closures (counters) ......) such that the following holds true: CL-USER> (defvar collection (permute-closures (list (make-counter 3) (make-counter 3)))) CL-USER> (funcall collection) (1 1) CL-USER> (funcall collection) (1 2) CL-USER> (funcall collection) (1 3) CL-USER> (funcall collection) (2 1) ... and so on. The way I had it designed originally was to add a 'pause' parameter to the initial counting lambda such that when iterating you can still call it and receive the old cached value if passed ":pause t", in hopes of making the permutation slightly cleaner. Also, while the example above is a simple list of two identical closures, the list can be an arbitrarily-complicated tree (which can be permuted in depth-first order, and the resulting permutation set would have the shape of the tree.). I had this implemented, but my solution wasn't very clean and am trying to poll how others would approach the problem. Thanks in advance.

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  • Udp server sending only 0 bytes of data

    - by mawia
    Hi all, This is a simple Udp server.I am trying to transmit data to some clients,but unfortunetly it is unable to transmit data.Though send is running quite successfully but it is returning with a return value meaning it has send nothing.On the client they are receiving but again obviously,zero bytes. void* UdpServerStreamToClients(void *fileToServe) { int sockfd,n=0,k; struct sockaddr_in servaddr,cliaddr; socklen_t len; char dataToSend[1000]; sockfd=socket(AF_INET,SOCK_DGRAM,0); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(32000); bind(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr)); FILE *fp; if((fp=fopen((char*)fileToServe,"r"))==NULL) { printf("can not open file "); perror("fopen"); exit(1); } int dataRead=1; while(dataRead) { len = sizeof(cliaddr); if((dataRead=fread(dataToSend,1,500,fp))<0) { perror("fread"); exit(1); } //sleep(2); for(list<clientInfo>::iterator it=clients.begin();it!=clients.end();it++) { cliaddr.sin_family = AF_INET; inet_aton(inet_ntoa(it->addr.sin_addr),&cliaddr.sin_addr); cliaddr.sin_port = htons(it->udp_port); n=sendto(sockfd,dataToSend,sizeof(dataToSend),0,(struct sockaddr *)&cliaddr,len); cout<<"number of bytes send by udp: "<< n << endl; printf("SEND this message %d : %s to %s :%d \n",n,dataToSend,inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)); } } } I am checking the value of sizeof(dataTosend) and it is pretty much as expected ie thousand ie the size of buffer. Are you people seeing some possible flaw in it. All of the help in this regard will be appreciated. Thanks!

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  • Parallelism on two duo-core processor system

    - by Qin
    I wrote a Java program that draw the Mandelbrot image. To make it interesting, I divided the for loop that calculates the color of each pixel into 2 halves; each half will be executed as a thread thus parallelizing the task. On a two core one cpu system, the performance of using two thread approach vs just one main thread is nearly two fold. My question is on a two dual-core processor system, will the parallelized task be split among different processor instead of just utilize the two core on one processor? I suppose the former scenario will be slower than the latter one simply because the latency of communicating between 2 CPU over the motherboard wires. Any ideas? Thanks

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  • HELP!! Implementing a search to match the specified author and displaying a book by the specified publisher

    - by Brian
    Hey guys! So i'm having problems with my assignment. I successfully got it to run multiple last names by the author, but now, I need to find all books by author, which means searching the collection for all books that match the specified author and I also need to find all books by publisher, which displays a list of books by the specified publisher. How would I implement this? Would I use string or vector? Any help will be much appreciated!

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  • Is there any interesting jobs available for C++ other than device drivers / firmwares developments?

    - by AKN
    Hi, Initially C was used for designing drivers / firmwares and all that. Right now this has been taken over by C++. Ok. Let me not deviate this question. I would like to know where else C++ is being used and how you see its future? You can also list out pros and cons of C++ compared to other languages. Would like to see a healthy and meaningful discussion on C++ current usage and its future?! Cheers! AKN

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  • Efficiently get the size of a parameter pack up to a certain index

    - by NmdMystery
    I want to be able to determine the number of bytes that are in a subset of a parameter pack from 0 to a given index. Right now I'm using a non-constexpr way of doing this. Below is my code: template <size_t index, typename... args> struct pack_size_index; template <size_t index, typename type_t, typename... args> struct pack_size_index <index, type_t, args...> { static const size_t index_v = index; static const size_t value(void) { if (index_v > 0) { return sizeof(type_t) + pack_size_index<index - 1, args...>::value(); } return 0; } }; template <size_t index> struct pack_size_index <index> { static const size_t index_v = index; static const size_t value(void) { return 0; } }; Usage: //output: 5 (equal to 1 + 4) std::cout << pack_size_index<2, bool, float, int, double>::value() << std::endl; //output: 20 (equal to 8 + 8 + 4) std::cout << pack_size_index<3, double, double, float, int>::value() << std::endl; This gets the job done, but this uses runtime comparison and the resulting executable increases in size rapidly whenever this is used. What's a less expensive way of doing this?

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  • Tools and environments supporting Domain Driven Design (DDD)

    - by anthares
    Hi everyone, I'm doing a kind of research on the topic "Domain Driven Design". My question is what tools (or maybe environments) do you use, that support this paradigm? I know that I can google it, but I wonder which of them actually work and are useful, since I have no experience with neither of them. I'm interesting mainly in the .NET Framework, but any other opinions are also welcome! Thanks !

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  • Linux Kernel - Integer to ASCII

    - by DRX-Z
    I need to convert an integer to it's ASCII representation from within the Linux Kernel. How can I do this? I can't find any built-in conversion methods. Are there any already in the kernel or do I need to add my own?

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  • Open source project. I want to participate in something

    - by user69514
    I am a senior in Computer Science. I want to be part of some open source project. I don't know what's available out there. Can anybody guide me? I'm good with Java, not that great with C and C++, but I know both. I also know some Cincom Smalltalk. Or if anyone has something good that they're working on I could help.

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  • Assign a static function to a variable in PHP

    - by Felipe Almeida
    I would like to assign a static function to a variable so that I can send it around as a parameter. For example: class Foo{ private static function privateStaticFunction($arg1,$arg2){ //compute stuff on the args } public static function publicStaticFunction($foo,$bar){ //works $var = function(){ //do stuff }; //also works $var = function($someArg,$someArg2){ //do stuff }; //Fatal error: Undefined class constant 'privateStaticFunction' $var = self::privateStaticMethod; //same error $var = Foo::privateStaticFunction; //compiles, but errors when I try to run $var() somewhere else, as expected //Fatal error: Call to private method Foo::privateStaticMethod() from context '' $var = function(){ return Foo::privateStaticMethod(); }; } } I've tried a few more variations but none of them worked. I don't even expect this sort of functional hacking to work with PHP but hey, who knows? Is it possible to do that in PHP or will I need to come up with some hack using eval? P.S.: LawnGnome on ##php mentioned something about it being possible to do what I want using array('Foo','privateStaticMethod') but I didn't understand what he meant and I didn't press him further as he looked busy.

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  • Abort early in a fold

    - by Heptic
    What's the best way to terminate a fold early? As a simplified example, imagine I want to sum up the numbers in an Iterable, but if I encounter something I'm not expecting (say an odd number) I might want to terminate. This is a first approximation def sumEvenNumbers(nums: Iterable[Int]): Option[Int] = { nums.foldLeft (Some(0): Option[Int]) { case (None, _) => None case (Some(s), n) if n % 2 == 0 => Some(s + n) case (Some(_), _) => None } } However, this solution is pretty ugly (as in, if I did a .foreach and a return -- it'd be much cleaner and clearer) and worst of all, it traverses the entire iterable even if it encounters a non-even number. So what would be the best way to write a fold like this, that terminates early? Should I just go and write this recursively, or is there a more accepted way?

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  • Does a syntax for this exist? In any language?

    - by Michael
    It seems pretty common to me to have an argument, in a dynamically typed language that is either an Object or a key to lookup that object. For instance when I'm working with a database I might have a method getMyRelatedStuff(person) All I really need to lookup the related stuff is the id of the person so my method could look like this in python: def getMyRelatedStuff(person_or_id): id = person_or_id.id if isinstance(person,User) else person_or_id #do some lookup Or going the other direction: def someFileStuff(file_or_name): file = file_or_name if hasattr(file,'write') else open(file_or_name)

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  • Solving the problem of finding parts which work well with each other

    - by dotnetdev
    Hi, I have a database of items. They are for cars and similar parts (eg cam/pistons) work better than others in different combinations (eg one product will work well with another, while another combination of 2 parts may not). There are so many possible permutations, what solutions apply to this problem? So far, I feel that these are possible approaches (Where I have question marks, something tells me these are solutions but I am not 100% confident they are). Neural networks (?) Collection-based approach (selection of parts in a collection for cam, and likewise for pistons in another collection, all work well with each other) Business rules engine (?) What are good ways to tackle this sort of problem? Thanks

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