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  • Function Overloading

    - by Sanju
    Let us suppose i have these three methods defined: int F1(int, int); int F1(float, float); Float F1(int, int); and i am calling method F1 here: Console.writeline(F1(5,6).ToString())); Which method it will call and why?

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  • True / false evaluation doesn't work as expected in Scheme

    - by ron
    I'm trying to compare two booleans : (if (equal? #f (string->number "123b")) "not a number" "indeed a number") When I run this in the command line of DrRacket I get "not a number" , however , when I put that piece of code in my larger code , the function doesn't return that string ("not a number") , here's the code : (define (testing x y z) (define badInput "ERROR") (if (equal? #f (string->number "123b")) "not a number" "indeed a number") (display x)) And from command line : (testing "123" 1 2) displays : 123 Why ? Furthermore , how can I return a value , whenever I choose ? Here is my "real" problem : I want to do some input check to the input of the user , but the thing is , that I want to return the error message if I need , before the code is executed , because if won't - then I would run the algorithm of my code for some incorrect input : (define (convert originalNumber s_oldBase s_newBase) (define badInput "ERROR") ; Input check - if one of the inputs is not a number then return ERROR (if (equal? #f (string->number originalNumber)) badInput) (if (equal? #f (string->number s_oldBase)) badInput) (if (equal? #f (string->number s_newBase)) badInput) (define oldBase (string->number s_oldBase)) (define newBase (string->number s_newBase)) (define outDecimal (convertIntoDecimal originalNumber oldBase)) (define result "") ; holds the new number (define remainder 0) ; remainder for each iteration (define whole 0) ; the whole number after dividing (define temp 0) (do() ((= outDecimal 0)) ; stop when the decimal value reaches 0 (set! whole (quotient outDecimal newBase)) ; calc the whole number (set! temp (* whole newBase)) (set! remainder (- outDecimal temp)) ; calc the remainder (set! result (appending result remainder)) ; append the result (set! outDecimal (+ whole 0)) ; set outDecimal = whole ) ; end of do (if (> 1 0) (string->number (list->string(reverse (string->list result))))) ) ;end of method This code won't work since it uses another method that I didn't attach to the post (but it's irrelevant to the problem . Please take a look at those three IF-s ... I want to return "ERROR" if the user put some incorrect value , for example (convert "23asb4" "b5" "9") Thanks

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  • Directly Jump to another C++ function

    - by maligree
    I'm porting a small academic OS from TriCore to ARM Cortex (Thumb-2 instruction set). For the scheduler to work, I sometimes need to JUMP directly to another function without modifying the stack nor the link register. On TriCore (or, rather, on tricore-g++), this wrapper template (for any three-argument-function) works: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { typedef void (* __attribute__((interrupt_handler)) Jump3)( A1, A2, A3); ( (Jump3)func )( a1, a2, a3 ); } //example for using the template: JUMP3( superDispatch, this, me, next ); This would generate the assembler instruction J (a.k.a. JUMP) instead of CALL, leaving the stack and CSAs unchanged when jumping to the (otherwise normal) C++ function superDispatch(SchedulerImplementation* obj, Task::Id from, Task::Id to). Now I need an equivalent behaviour on ARM Cortex (or, rather, for arm-none-linux-gnueabi-g++), i.e. generate a B (a.k.a. BRANCH) instruction instead of BLX (a.k.a. BRANCH with link and exchange). But there is no interrupt_handler attribute for arm-g++ and I could not find any equivalent attribute. So I tried to resort to asm volatile and writing the asm code directly: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { asm volatile ( "mov.w r0, %1;" "mov.w r1, %2;" "mov.w r2, %3;" "b %0;" : : "r"(func), "r"(a1), "r"(a2), "r"(a3) : "r0", "r1", "r2" ); } So far, so good, in my theory, at least. Thumb-2 requires function arguments to be passed in the registers, i.e. r0..r2 in this case, so it should work. But then the linker dies with undefined reference to `r6' on the closing bracket of the asm statement ... and I don't know what to make of it. OK, I'm not the expert in C++, and the asm syntax is not very straightforward... so has anybody got a hint for me? A hint to the correct __attribute__ for arm-g++ would be one way, a hint to fix the asm code would be another. Another way maybe would be to tell the compiler that a1..a3 should already be in the registers r0..r2 when the asm statement is entered (I looked into that a bit, but did not find any hint).

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  • Waiting for data via select not working

    - by BSchlinker
    I'm currently working on a project which involves multiple clients connected to a server and waiting for data. I'm using select and monitoring the connection for incoming data. However, the client just continues to print nothing, acting as if select has discovered incoming data. Perhaps I'm attacking this wrong? For the first piece of data the server does send, it is displayed correctly. However, the server then disconnects and the client continues to spew blank lines. FD_ZERO(&readnet); FD_SET(sockfd, &readnet); while(1){ rv = select(socketdescrip, &readnet, NULL, NULL, &timeout); if (rv == -1) { perror("select"); // error occurred in select() } else if (rv == 0) { printf("Connection timeout! No data after 10 seconds.\n"); } else { // one or both of the descriptors have data if (FD_ISSET(sockfd, &readnet)) { numbytes = recv(sockfd, buf, sizeof buf, 0); printf("Data Received\n"); buf[numbytes] = '\0'; printf("client: received '%s'\n",buf); sleep(10); } } }

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  • Challenging yourself as a programmer?

    - by Kevin
    We used to be a Coldfusion development shop before hopping over to PHP in 2008, now we primarily develop custom Drupal websites. I enjoyed going from CF to PHP, but I feel like I am getting a bit stale. I have been looking at different things like Ruby, Python, Obj C (iPhone). The problem is, there just isn't enough time in the day. What would be a fun new thing to learn that would refresh me a bit and challenge myself to learn more?

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  • Sending emails?

    - by Kaep
    Hi i saw a post explaining how to send emails in python. But my problem is finding a server that will send my email on.. I read about setting one up and i read that it is a complicated process.. Can anyone help me find a server or give me a tip to set one up myself? Thanks!

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  • suggestions on syntax to express mathematical formula concisely

    - by aaa
    hello. I am developing functional domain specific embedded language within C++ to translate formulas into working code as concisely and accurately as possible. I post prototype in the comment, it is about 2 hundred lines long. Right now my language looks something like this (well, actually is going to look like): // implies two nested loops j=0:N, i=0,j (range(i) < j < N)[T(i,j) = (T(i,j) - T(j,i))/e(i+j)]; // implies summation over above expression sum(range(i) < j < N))[(T(i,j) - T(j,i))/e(i+j)]; I am looking for possible syntax improvements/extensions or just different ideas about expressing mathematical formulas as clearly and precisely as possible (in any language, not just C++). Can you give me some syntax examples relating to my question which can be accomplished in your language of choice which consider useful. In particular, if you have some ideas about how to translate the above code segments, I would be happy to hear them. Thank you just to clarify and give actual formula, my short-term goal is to express the following expression concisely where values in <> are already computed as 4-dimensional array

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  • Creating a database instance in C#

    - by wonea
    Is it possible to create a sql database instance with C# code. I have no problem adding a database to an existing SQL instance, for example WONEA\SQLEXPRESS but for creating another SQL instance such as WONEA\SQLEXPRESSTEST I'm a little stumped. Help!

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  • How can I manually uninstall .NET Framework Beta 2?

    - by DannyAsher
    Uninstalled VS2010 Beta 2. Uninstalled .NET Framework 4 Extended Beta 2. On attempting to uninstall .NET Framework 4 Client Profile Beta 2. I get Blocking Issues: You must uninstall the .NET Framework 4 Extended Beta 2 before you uninstall the .NET Framework 4 Client Profile Beta 2. On attempting to reinstall Framework 4 Beta 2 I get: Details: Same or higher version of .NET Framework 4 Beta 2 has already been installed on this computer. Please help! Can I simply remove registry entries and the C:\WINDOWS\Microsoft.NET\Framework\v4.0.21006 directory?

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  • Client/Server communication via internet

    - by user957829
    Hi, Which is the best solution to communicate bidirectionally between a remote server and a client behind an internet box? UPnP with Sockets. HTTPS/Database Server and the client make 1 request every Xsec to know if there is new data. Client opens 1 connection on the server and it maintains open to make a tunnel. Thanks in advance for your help

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  • Regarding PID Shell Script

    - by arav
    I am calling another shell script testarg.sh within my main script. the logfiles of testarg.sh are stored in $CUSTLOGS in the below format testarg.DDMONYY.PID.log example: testarg.09Jun10.21165.log In the main script after the testarg process gets completed i need to grep the log file for the text "ERROR" and "COMPLETED SUCCESSFULLY". How do i get the PID of the process and combine with DDMONYY for grepping. Also i need to check whether file exists before grepping $CUSTBIN/testarg.sh $CUSTBIN/testarg.sh rc=$? if [ $rc -ne 0 ]; then return $CODE_WARN fi

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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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  • After C++ - Python or Java?

    - by carleeto
    I'm fast approaching the point in my coding where I would like to quickly write object oriented code in languages other than C++ for a variety of reasons. After a lot of research, my choices have pretty much narrowed down to Python and Java. I'm leaning towards Python because of its relationship to C, but with Java, from what I can see, I get a good introduction to using and creating test suites with Eclipse - there is also Processing which is pulling me towards Java. I'm not the kind of guy to tackle two languages at once, so which one would you recommend and why? What I want at the end is to have an additional language I can use for rapid development. Ease of learning isn't important to me as I'm willing to put in the time regardless. Ability to use the new language widely is.

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  • Is it faster to count down than it is to count up?

    - by Bob
    Our computer science teacher once said that for some reason it is more efficient to count down that count up. For example if you need to use a FOR loop and the loop index is not used somewhere (like printing a line of N * to the screen) I mean that code like this : for (i=N; i>=0; i--) putchar('*'); is better than: for (i=0; i<N; i++) putchar('*'); Is it really true? and if so does anyone know why?

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  • Binding on a port with netpipes/netcat

    - by mindas
    I am trying to write a simple bash script that is listening on a port and responding with a trivial HTTP response. My specific issue is that I am not sure if the port is available and in case of bind failure I fall back to next port until bind succeeds. So far to me the easiest way to achieve this was something like: for (( i=$PORT_BASE; i < $(($PORT_BASE+$PORT_RANGE)); i++ )) do if [ $DEBUG -eq 1 ] ; then echo trying to bind on $i fi /usr/bin/faucet $i --out --daemon echo test 2>/dev/null if [ $? -eq 0 ] ; then #success? port=$i if [ $DEBUG -eq 1 ] ; then echo "bound on port $port" fi break fi done Here I am using faucet from netpipes Ubuntu package. The problem with this is that if I simply print "test" to the output, curl complains about non-standard HTTP response (error code 18). That's fair enough as I don't print HTTP-compatible response. If I replace echo test with echo -ne "HTTP/1.0 200 OK\r\n\r\ntest", curl still complains: user@server:$ faucet 10020 --out --daemon echo -ne "HTTP/1.0 200 OK\r\n\r\ntest" ... user@client:$ curl ip.of.the.server:10020 curl: (56) Failure when receiving data from the peer I think the problem lies in how faucet is printing the response and handling the connection. For example if I do the server side in netcat, curl works fine: user@server:$ echo -ne "HTTP/1.0 200 OK\r\n\r\ntest\r\n" | nc -l 10020 ... user@client:$ curl ip.of.the.server:10020 test user@client:$ I would be more than happy to replace faucet with netcat in my main script, but the problem is that I want to spawn independent server process to be able to run client from the same base shell. faucet has a very handy --daemon parameter as it forks to background and I can use $? (exit status code) to check if bind succeeded. If I was to use netcat for a similar purpose, I would have to fork it using & and $? would not work. Does anybody know why faucet isn't responding correctly in this particular case and/or can suggest a solution to this problem. I am not married neither to faucet nor netcat but would like the solution to be implemented using bash or it's utilities (as opposed to write something in yet another scripting language, such as Perl or Python).

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  • an error "variable of field declared void"

    - by lego69
    I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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  • Does anyone else think instance variables are problematic in database-backed applications?

    - by Ben Aston
    It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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