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  • help Implementing Object Oriented ansi-C approach??

    - by No Money
    Hey there, I am an Intermediate programmer in Java and know some of the basics in C++. I recently started to scam over "C language" [please note that i emphasized on C language and want to stick with C as i found it to be a perfect tool, so no need for suggestions focusing on why should i move back to C++ or Java]. Moving on, I code an Object Oriented approach in C but kindda scramble with the pointers part. Please understand that I am just a noob trying to extend my knowledge beyond what i learned in High School. Here is my code..... #include <stdio.h> typedef struct per{ int privateint; char *privateString; struct per (*New) (); void (*deleteperOBJ) (struct t_person *); void (*setperNumber) ((struct*) t_person,int); void (*setperString) ((struct*) t_person,char *); void (*dumpperState) ((struct*) t_person); }t_person; void setperNumber(t_person *const per,int num){ if(per==NULL) return; per->privateint=num; } void setperString(t_person *const per,char *string){ if(per==NULL) return; per->privateString=string; } void dumpperState(t_person *const per){ if(per==NULL) return; printf("value of private int==%d\n", per->privateint); printf("value of private string==%s\n", per->privateString); } void deleteperOBJ(struct t_person *const per){ free((void*)t_person->per); t_person ->per = NULL; } main(){ t_person *const per = (struct*) malloc(sizeof(t_person)); per = t_person -> struct per -> New(); per -> setperNumber (t_person *per, 123); per -> setperString(t_person *per, "No money"); dumpperState(t_person *per); deleteperOBJ(t_person *per); } Just to warn you, this program has several errors and since I am a beginner I couldn't help except to post this thread as a question. I am looking forward for assistance. Thanks in advance.

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  • Matching array elements to get an array element at another index

    - by bccarlso
    I have a PHP array that I'm using to generate an HTML form. The PHP array is this: <?php $vdb = array ( array( "Alabama", 275), array( "Alaska", 197), array( "Arizona", 3322)); ?> The PHP to generate the HTML form is below. I need to have the value be the name of the state, because there is some AJAX I'm using to display which states a user has chosen. <?php echo "<table border='1'><thead><tr><th></th><th>State</th><th>Contacts</th><th>Email</th></tr></thead>"; for ($row = 0; $row < 42; $row++) { echo "<tr><td class='input_button'><input type='checkbox' name='vdb[]' value='".$vdb[$row][0]."' title='".$vdb[$row][1]."' /></td>"; echo "<td>".$vdb[$row][0]."</td>"; echo "<td>".$vdb[$row][1]."</td>"; } echo "</table>"; ?> What I'm trying to do is, on submission of the form, with the states the user selected, loop through the PHP array and total the numbers from the selected states. So if I checked Alabama and Alaska, I'd want to add 275 + 197. This is what I thought would have worked, but it's not: <?php $vendors = array(); if (isset($_POST["vdb"])) { $vendors = $_POST["vdb"]; } $ven_i = 0; $ven_j = 0; $ven_total = 0; foreach ($vendors as $value) { foreach ($vdb as $vdb_value) { if ($vendors[$ven_i] == $vdb[$ven_j][0]) { $ven_total += $vdb[$ven_j][1]; } $ven_j++; } $ven_i++; } ?> and then $ven_total should be the total I'm looking for. However, $ven_total just ends up being the first checkbox selected, and it ignores the rest. I am doing this correctly with the AJAX, displaying the total on the front end, but I don't know how to pass that on to the form submission. I'd rather not using GET and URL variables, because a user could type something into the URL and modify the count. Any idea what I'm doing wrong, or a better way to approach this that I would be able to understand? (Very much a novice programmer.)

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  • How to check for palindrome using Python logic

    - by DrOnline
    My background is only a 6 month college class in basic C/C++, and I'm trying to convert to Python. I may be talking nonsense, but it seems to me C, at least at my level, is very for-loop intensive. I solve most problems with these loops. And it seems to me the biggest mistake people do when going from C to Python is trying to implement C logic using Python, which makes things run slowly, and it's just not making the most of the language. I see on this website: http://hyperpolyglot.org/scripting (serach for "c-style for", that Python doesn't have C-style for loops. Might be outdated, but I interpret it to mean Python has its own methods for this. I've tried looking around, I can't find much up to date (Python 3) advice for this. How can I solve a palindrome challenge in Python, without using the for loop? I've done this in C in class, but I want to do it in Python, on a personal basis. The problem is from the Euler Project, great site btw. def isPalindrome(n): lst = [int(n) for n in str(n)] l=len(lst) if l==0 || l==1: return True elif len(lst)%2==0: for k in range (l) ##### else: while (k<=((l-1)/2)): if (list[]): ##### for i in range (999, 100, -1): for j in range (999,100, -1): if isPalindrome(i*j): print(i*j) break I'm missing a lot of code here. The five hashes are just reminders for myself. Concrete questions: 1) In C, I would make a for loop comparing index 0 to index max, and then index 0+1 with max-1, until something something. How to best do this in Python? 2) My for loop (in in range (999, 100, -1), is this a bad way to do it in Python? 3) Does anybody have any good advice, or good websites or resources for people in my position? I'm not a programmer, I don't aspire to be one, I just want to learn enough so that when I write my bachelor's degree thesis (electrical engineering), I don't have to simultaneously LEARN an applicable programming language while trying to obtain good results in the project. "How to go from basic C to great application of Python", that sort of thing. 4) Any specific bits of code to make a great solution to this problem would also be appreciated, I need to learn good algorithms.. I am envisioning 3 situations. If the value is zero or single digit, if it is of odd length, and if it is of even length. I was planning to write for loops... PS: The problem is: Find the highest value product of two 3 digit integers that is also a palindrome.

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  • Need a fast programming language that can drive two printers

    - by Pete
    I have a rather unusual application that isn't working the way I need, and I hope someone here will have some suggestions or at least a direction to investigate. We have a museum exhibit that has a computer at the entrance driving two small receipt printers. There are two buttons on a console, wired to the left and right buttons of a disemboweled mouse. The two printers and associated buttons are for girls and boys, each button does a random selection from a database of names and prints a small ticket on the appropriate printer with a graphic image, a few words about the exhibit and the randomly chosen name. Conceptually all is well, but it hangs quite often. I got the project at the last minute, because the original designer got bogged down and couldn't deliver, so the exhibit's author asked me the day before opening, whether I could write something that would work. I did it in Word, since I am an experienced VBA programmer. Several other avenues I attempted first all lead to dead ends - one couldn't do graphics, another couldn't handle two printers, yet another couldn't change fonts and so on. The problem is that it simply isn't fast enough - Word can only drive one printer at a time and changing the active printer takes a long time. Not by office standards, where a second or two of delay before a printer starts working on your document is not an issue, but here I need more or less instant response. If kids press a button and nothing happens, they press it over and over until something does happen, resulting in maybe half a dozen commands being sent before the printer starts reacting. Sometimes it jams the program completely, since boys and girls will be pressing the two buttons simultaneously and Word locks up, and even when it doesn't jam, the printers then spit out a stream of tickets, making a mess. The kids start squabbling over which ticket is whose, pulling them out of the printers, snarling the paper tape, jamming the printer and generally making a mess of the whole affair, often necessitating the exhibit caretakers having to restart the computer and clear torn bits of paper out the printers. What I need is some sort of fast programming language that can drive two printers *-simultaneously-*, not the MSOffice claptrap of having to switch the active printer, that can react to both left and right mouse button click events, can print a small graphic image and can print in different font sizes and styles and. I don't need many, but it's not all in one typeface. Can anyone suggest what I might use for this? I don't even know if it's possible at all under Windows, whether the "single active printer" garbage is an Office artifact, or a Windows restriction. My little Commodore-64 twenty-five years ago had two printers attached to it and drove both simultaneously with no difficulties - it doesn't seem to me it should be such an impossible requirement today.

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  • Do You Really Know Your Programming Languages?

    - by Kristopher Johnson
    I am often amazed at how little some of my colleagues know or care about their craft. Something that constantly frustrates me is that people don't want to learn any more than they need to about the programming languages they use every day. Many programmers seem content to learn some pidgin sub-dialect, and stick with that. If they see a keyword or construct that they aren't familiar with, they'll complain that the code is "tricky." What would you think of a civil engineer who shied away from calculus because it had "all those tricky math symbols?" I'm not suggesting that we all need to become "language lawyers." But if you make your living as a programmer, and claim to be a competent user of language X, then I think at a minimum you should know the following: Do you know the keywords of the language and what they do? What are the valid syntactic forms? How are memory, files, and other operating system resources managed? Where is the official language specification and library reference for the language? The last one is the one that really gets me. Many programmers seem to have no idea that there is a "specification" or "standard" for any particular language. I still talk to people who think that Microsoft invented C++, and that if a program doesn't compile under VC6, it's not a valid C++ program. Programmers these days have it easy when it comes to obtaining specs. Newer languages like C#, Java, Python, Ruby, etc. all have their documentation available for free from the vendors' web sites. Older languages and platforms often have standards controlled by standards bodies that demand payment for specs, but even that shouldn't be a deterrent: the C++ standard is available from ISO for $30 (and why am I the only person I know who has a copy?). Programming is hard enough even when you do know the language. If you don't, I don't see how you have a chance. What do the rest of you think? Am I right, or should we all be content with the typical level of programming language expertise? Update: Several great comments here. Thanks. A couple of people hit on something that I didn't think about: What really irks me is not the lack of knowledge, but the lack of curiosity and willingness to learn. It seems some people don't have any time to hone their craft, but they have plenty of time to write lots of bad code. And I don't expect people to be able to recite a list of keywords or EBNF expressions, but I do expect that when they see some code, they should have some inkling of what it does. Few people have complete knowledge of every dark corner of their language or platform, but everyone should at least know enough that when they see something unfamiliar, they will know how to get whatever additional information they need to understand it.

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  • Chrome extension - Localstorage not working

    - by Bjarki Jonasson
    I'm writing a Chrome extension that uses a content script to modify certain parts of a website. The content script worked fine until I tried to add an options page to my extension. Right now I'm using an options.html file to save user preferences to localstorage, as you can see here: <html> <head><title>Options</title></head> <script type="text/javascript"> function save_options() { var select = document.getElementById("width"); var width = select.children[select.selectedIndex].value; localStorage["site_width"] = width; } function restore_options() { var fwidth = localStorage["site_width"]; if (!fwidth) { return; } var select = document.getElementById("width"); for (var i = 0; i < select.children.length; i++) { var child = select.children[i]; if (child.value == fwidth) { child.selected = "true"; break; } } } </script> <body onload="restore_options()"> Width: <select id="width"> <option value="100%">100%</option> <option value="90%">90%</option> <option value="80%">80%</option> <option value="70%">70%</option> </select> <br> <button onclick="save_options()">Save</button> </body> </html> I also have a background.html file to handle the communication between the content script and the localstorage: <html> <script type="text/javascript"> chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { if (request.method == "siteWidth") sendResponse({status: localStorage["site_width"]}); else sendResponse({}); }); </script> </html> Then there's the actual content script that looks like this: var Width; chrome.extension.sendRequest({method: "siteWidth"}, function(response) { width = response.status; }); None of that code actually works. It looks solid enough to me but I'm not a very experienced programmer so I might be wrong. Could someone explain localstorage to me in layman's terms?

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  • Implementing Object Oriented: ansi-C approach

    - by No Money
    Hey there, I am an Intermediate programmer in Java and know some of the basics in C++. I recently started to scam over "C language" [please note that i emphasized on C language and want to stick with C as i found it to be a perfect tool, so no need for suggestions focusing on why should i move back to C++ or Java or any other crappy language (e.g: C#)]. Moving on, I code an Object Oriented approach in C but kindda scramble with the pointers part. Please understand that I am just a noob trying to extend my knowledge beyond what i learned in High School. Here is my code..... #include <stdio.h> typedef struct per{ int privateint; char *privateString; struct per (*New) (); void (*deleteperOBJ) (struct t_person *); void (*setperNumber) ((struct*) t_person,int); void (*setperString) ((struct*) t_person,char *); void (*dumpperState) ((struct*) t_person); }t_person; void setperNumber(t_person *const per,int num){ if(per==NULL) return; per->privateint=num; } void setperString(t_person *const per,char *string){ if(per==NULL) return; per->privateString=string; } void dumpperState(t_person *const per){ if(per==NULL) return; printf("value of private int==%d\n", per->privateint); printf("value of private string==%s\n", per->privateString); } void deleteperOBJ(struct t_person *const per){ free((void*)t_person->per); t_person ->per = NULL; } main(){ t_person *const per = (struct*) malloc(sizeof(t_person)); per = t_person -> struct per -> New(); per -> setperNumber (t_person *per, 123); per -> setperString(t_person *per, "No money"); dumpperState(t_person *per); deleteperOBJ(t_person *per); } Just to warn you, this program has several errors and since I am a beginner I couldn't help except to post this thread as a question. I am looking forward for assistance. Thanks in advance.

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  • Coping with feelings of technical mediocrity

    - by Karim
    As I've progressed as a programmer, I noticed more nuance and areas I could study in depth. In part, I've come to think of myself from, at one point, a "guru" to now much less, even mediocre or inadequate. Is this normal, or is it a sign of a destructive excessive ambition? Background I started to program when I was still a kid, I had about 10 or 11 years. I really enjoy my work and never get bored from it. It's amazing how somebody could be paid for what he really likes to do and would be doing it anyway even for free. When I first started to program, I was feeling proud of what I was doing, each application I built was for me a success and after 2-3 year I had a feeling that I'm a coding guru. It was a nice feeling. ;-) But the more I was in the field and the more types of software I started to develop, I was starting to have a feeling that I'm completely wrong in thinking I'm a guru. I felt that I'm not even a mediocre developer. Each new field I start to work on is giving me this feeling. Like when I once developed a device driver for a client, I saw how much I need to learn about device drivers. When I developed a video filter for an application, I saw how much do I still need to learn about DirectShow, Color Spaces, and all the theory behind that. The worst thing was when I started to learn algorithms. It was several years ago. I knew then the basic structures and algorithms like the sorting, some types of trees, some hashtables, strings, etc. and when I really wanted to learn a group of structures I learned about 5-6 new types and saw that in fact even this small group has several hundred subtypes of structures. It's depressing how little time people have in their lives to learn all this stuff. I'm now a software developer with about 10 years of experience and I still feel that I'm not a proficient developer when I think about things that others do in the industry.

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  • C++ Class Access Specifier Verbosity

    - by PolyTex
    A "traditional" C++ class (just some random declarations) might resemble the following: class Foo { public: Foo(); explicit Foo(const std::string&); ~Foo(); enum FooState { Idle, Busy, Unknown }; FooState GetState() const; bool GetBar() const; void SetBaz(int); private: struct FooPartialImpl; void HelperFunction1(); void HelperFunction2(); void HelperFunction3(); FooPartialImpl* m_impl; // smart ptr FooState m_state; bool m_bar; int m_baz; }; I always found this type of access level specification ugly and difficult to follow if the original programmer didn't organize his "access regions" neatly. Taking a look at the same snippet in a Java/C# style, we get: class Foo { public: Foo(); public: explicit Foo(const std::string&); public: ~Foo(); public: enum FooState { Idle, Busy, Unknown }; public: FooState GetState() const; public: bool GetBar() const; public: void SetBaz(int); private: struct FooPartialImpl; private: void HelperFunction1(); private: void HelperFunction2(); private: void HelperFunction3(); private: FooPartialImpl* m_impl; // smart ptr private: FooState m_state; private: bool m_bar; private: int m_baz; }; In my opinion, this is much easier to read in a header because the access specifier is right next to the target, and not a bunch of lines away. I found this especially true when working with header-only template code that wasn't separated into the usual "*.hpp/*.inl" pair. In that scenario, the size of the function implementations overpowered this small but important information. My question is simple and stems from the fact that I've never seen anyone else actively do this in their C++ code. Assuming that I don't have a "Class View" capable IDE, are there any obvious drawbacks to using this level of verbosity? Any other style recommendations are welcome!

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  • Java loading user-specified classes at runtime

    - by user349043
    I'm working on robot simulation in Java (a Swing application). I have an abstract class "Robot" from which different types of Robots are derived, e.g. public class StupidRobot extends Robot { int m_stupidness; int m_insanityLevel; ... } public class AngryRobot extends Robot { float m_aggression; ... } As you can see, each Robot subclass has a different set of parameters. What I would like to do is control the simulation setup in the initial UI. Choose the number and type of Robots, give it a name, fill in the parameters etc. This is one of those times where being such a dinosaur programmer, and new to Java, I wonder if there is some higher level stuff/thinking that could help me here. So here is what I've got: (1) User Interface Scrolling list of Robot types on the left. "Add " and "<< Remove" buttons in the middle. Default-named scrolling list of Robots on the right. "Set Parameters" button underneath. (So if you wanted an AngryRobot, you'd select AngryRobot on the left list, click "Add" and "AngryRobot1" would show up on the right.) When selecting a Robot on the right, click "Set Parameters..." button which would call yet another model dialog where you'd fill in the parameters. Different dialog called for each Robot type. (2) Data structures an implementation As an end-product I think a HashMap would be most convenient. The keys would be Robot types and the accompanying object would be all of the parameters. The initializer could just retrieve each item one and a time and instantiate. Here's what the data structures would look like: enum ROBOT_TYPE {STUPID, ANGRY, etc} public class RobotInitializer { public ROBOT_TYPE m_type; public string m_name; public int[] m_int_params; public float[] m_float_params; etc. The initializer's constructor would create the appropriate length parameter arrays based on the type: public RobotInitializer(ROBOT_TYPE type, int[] int_array, float[] float_array, etc){ switch (type){ case STUPID: m_int_params = new int[STUPID_INT_PARAM_LENGTH]; System.arraycopy(int_array,0,m_int_params,0,STUPID_INT_PARAM_LENGTH); etc. Once all the RobotInitializers are instantiated, they are added to the HashMap. Iterating through the HashMap, the simulation initializer takes items from the Hashmap and instantiates the appropriate Robots. Is this reasonable? If not, how can it be improved? Thanks

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  • A case-insensitive related implementation problem

    - by Robert
    Hi All, I am going through a final refinement posted by the client, which needs me to do a case-insesitive query. I will basically walk through how this simple program works. First of all, in my Java class, I did a fairly simple webpage parsing: title=(String)results.get("title"); doc = docBuilder.parse("http://" + server + ":" + port + "/exist/rest/db/wb/xql/media_lookup.xql?" + "&title=" + title); This Java statement references an XQuery file "media_lookup.xql" which is stored on localhost, and the only parameter we are passing is the string "title". Secondly, let's take at look at that XQuery file: $title := request:get-parameter('title',""), $mediaNodes := doc('/db/wb/portfolio/media_data.xml'), $query := $mediaNodes//media[contains(title,$title)], Then it will evaluate that query. This XQuery will get the "title" parameter that are passes from our Java class, and query the "media_data" xml file stored in the database, which contains a bunch of media nodes with a 'title' element node. As you may expect, this simple query will just match those media nodes whose 'title' element contains a substring of what the value of string 'title' is. So if our 'title' is "Chi", it will return media nodes whose title may be "Chicago" or "Chicken". The refinment request posted by the client is that there should be NO case-sensitivity. The very intuitive way is to modify the XQuery statement by using a lower-case funtion in it, like: $query := $mediaNodes//media[contains(lower-case(title/text(),lower-case($title))], However, the question comes: this modified query will run my machine into memory overflow. Since my "media_data.xml" is quite huge and contains thouands of millions of media nodes, I assume the lower-case() function will run on each of the entries, thus causing the machine to crash. I've talked with some experienced XQuery programmer, and they think I should use an index to solve this problem, and I will definitely research into that. But before that, I am just posting this problem here to get other ideas or any suggestions, do you think any other way may help? for example, could I tweak the Java parse statement to realize the case-insensitivity? Since I think I saw some people did some string concatination by using "contains." in Java before passing it to the server. Any idea or help is welcomed, thanks in advance.

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  • web design PSD to html -> more direct ways?

    - by Assembler
    At work I see one colleague designing a site in Photoshop/Fireworks, I see another taking this data, slicing it up and using Dreamweaver to rebuild the same from scratch. It seems like too much mucking around! I know that Photoshop can output a tables based HTML, and Fireworks will create divs with absolute positioning; neither appear to be very helpful. Admittedly, I haven't tried much of (DW/FW) (CS4/CS3) since becoming a programmer, so I don't know if new versions are addressing this work flow issue, but are we still double handling things? Can we attach some sort of layout metadata (this is a rollover button, this will be a SWF, this will be text, this logo will hide "xyz" <h1> text etc) to slices to aid in layout generation? are there some secret tools which assist in this conversion process? Or are we still restricted to doing things by hand? The frustration continues when said hand built page needs to be reworked again to fit Smarty Templates/Wordpress/generic CMS. I acknowledge that designers need to be free of systems to be able to do whatever, but most conventional sites have: a header with navigation a sidebar with more links the main content part maybe another sidebar a footer Given the similarity of a lot of components, shouldn't there be a more systematic approach to going from sliced designs to functional HTML? Or am I over-simplifying things? -edit- Mmmmm.... I suppose I will accept an answer, but they weren't really what I was looking for. It just seems like designing the DOM is a bit of holy grail ("It's only a model!"), and maybe with all the "groovy" things you can do with HTML and Javascript, it would be mighty hard work, but with a set of constraints (that 960 stuff looks interesting), some well designed reset style sheets and a bit of... fairy dust? we should be able to improve the work flow. Photoshop's tables by themselves are pretty much useless, I agree, but surely we can take this data, and then select a group of cells and say "right, this is a text div, overflow:auto" or "these cells are an image block, style it with the same height/width as the selected area". Admittedly here at work there are other elephants in the room that need to make their formal introductions to management, but some parts of the designpage workflow seem... uneducated at best.

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  • Are there any platforms where using structure copy on an fd_set (for select() or pselect()) causes p

    - by Jonathan Leffler
    The select() and pselect() system calls modify their arguments (the 'struct fd_set *' arguments), so the input value tells the system which file descriptors to check and the return values tell the programmer which file descriptors are currently usable. If you are going to call them repeatedly for the same set of file descriptors, you need to ensure that you have a fresh copy of the descriptors for each call. The obvious way to do that is to use a structure copy: struct fd_set ref_set_rd; struct fd_set ref_set_wr; struct fd_set ref_set_er; ... ...code to set the reference fd_set_xx values... ... while (!done) { struct fd_set act_set_rd = ref_set_rd; struct fd_set act_set_wr = ref_set_wr; struct fd_set act_set_er = ref_set_er; int bits_set = select(max_fd, &act_set_rd, &act_set_wr, &act_set_er, &timeout); if (bits_set > 0) { ...process the output values of act_set_xx... } } My question: Are there any platforms where it is not safe to do a structure copy of the struct fd_set values as shown? I'm concerned lest there be hidden memory allocation or anything unexpected like that. (There are macros/functions FD_SET(), FD_CLR(), FD_ZERO() and FD_ISSET() to mask the internals from the application.) I can see that MacOS X (Darwin) is safe; other BSD-based systems are likely to be safe, therefore. You can help by documenting other systems that you know are safe in your answers. (I do have minor concerns about how well the struct fd_set would work with more than 8192 open file descriptors - the default maximum number of open files is only 256, but the maximum number is 'unlimited'. Also, since the structures are 1 KB, the copying code is not dreadfully efficient, but then running through a list of file descriptors to recreate the input mask on each cycle is not necessarily efficient either. Maybe you can't do select() when you have that many file descriptors open, though that is when you are most likely to need the functionality.) There's a related SO question - asking about 'poll() vs select()' which addresses a different set of issues from this question.

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  • Why do we have reinterpret_cast in C++ when two chained static_cast can do it's job?

    - by Nawaz
    Say I want to cast A* to char* and vice-versa, we have two choices (I mean, many of us think we've two choices, because both seems to work! Hence the confusion!): struct A { int age; char name[128]; }; A a; char *buffer = static_cast<char*>(static_cast<void*>(&a)); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 Both work fine. //convert back A *pA = static_cast<A*>(static_cast<void*>(buffer)); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Even this works fine! So why do we have reinterpret_cast in C++ when two chained static_cast can do it's job? Some of you might think this topic is a duplicate of the previous topics such as listed at the bottom of this post, but it's not. Those topics discuss only theoretically, but none of them gives even a single example demonstrating why reintepret_cast is really needed, and two static_cast would surely fail. I agree, one static_cast would fail. But how about two? If the syntax of two chained static_cast looks cumbersome, then we can write a function template to make it more programmer-friendly: template<class To, class From> To any_cast(From v) { return static_cast<To>(static_cast<void*>(v)); } And then we can use this, as: char *buffer = any_cast<char*>(&a); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 //convert back A *pA = any_cast<A*>(buffer); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Also, see this situation where any_cast can be useful: Proper casting for fstream read and write member functions. So my question basically is, Why do we have reinterpret_cast in C++? Please show me even a single example where two chained static_cast would surely fail to do the same job? Which cast to use; static_cast or reinterpret_cast? Cast from Void* to TYPE* : static_cast or reinterpret_cast

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  • Create a Counter within a For-Loop?

    - by Todd Hartman
    I am a novice programmer and apologize upfront for the complicated question. I am trying to create a lexical decision task for experimental research, in which respondents must decide if a series of letters presented on the screen make a "word" or "not a word". Everything works reasonably well except for the bit where I want to randomly select a word (category A) or nonword (category B) for each of 80 trials from a separate input file (input.txt). The randomization works, but some elements from each list (category A or B) are skipped because I have used "round.catIndex = j;" where "j" is a loop for each successive trial. Because some trials randomly select from Category A and other from Category B, "j" does not move successively down the list for each category. Instead, elements from the Category A list may be selected from something like 1, 2, 5, 8, 9, 10, and so on (it varies each time because of the randomization). To make a long story short(!), how do I create a counter that will work within the for-loop for each trial, so that every word and nonword from Category A and B, respectively, will be used for the lexical decision task? Everything I have tried thus far does not work properly or breaks the javascript entirely. Below is my code snippet and the full code is available at http://50.17.194.59/LDT/trunk/LDT.js. Also, the full lexical decision task can be accessed at http://50.17.194.59/LDT/trunk/LDT.php. Thanks! function initRounds() { numlst = []; for (var k = 0; k<numrounds; k++) { if (k % 2 == 0) numlst[k] = 0; else numlst[k] = 1; } numlst.sort(function() {return 0.5 - Math.random()}) for (var j = 0; j<numrounds; j++) { var round = new LDTround(); if (numlst[j] == 0) { round.category = input.catA.datalabel; } else if (numlst[j] == 1) { round.category = input.catB.datalabel; } // pick a category & stimulus if (round.category == input.catA.datalabel) { round.itemtype = input.catA.itemtype; round.correct = 1; round.catIndex = j; } else if (round.category == input.catB.datalabel) { round.itemtype = input.catB.itemtype; round.correct = 2; round.catIndex = j; } roundArray[i].push(round); } return roundArray; }

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  • How do I write object classes effectively when dealing with table joins?

    - by Chris
    I should start by saying I'm not now, nor do I have any delusions I'll ever be a professional programmer so most of my skills have been learned from experience very much as a hobby. I learned PHP as it seemed a good simple introduction in certain areas and it allowed me to design simple web applications. When I learned about objects, classes etc the tutor's basic examnples covered the idea that as a rule of thumb each database table should have its own class. While that worked well for the photo gallery project we wrote, as it had very simple mysql queries, it's not working so well now my projects are getting more complex. If I require data from two separate tables which require a table join I've instead been ignoring the class altogether and handling it on a case by case basis, OR, even worse been combining some of the data into the class and the rest as a separate entity and doing two queries, which to me seems inefficient. As an example, when viewing content on a forum I wrote, if you view a thread, I retrieve data from the threads table, the posts table and the user table. The queries from the user and posts table are retrieved via a join and not instantiated as an object, whereas the thread data is called using my Threads class. So how do I get from my current state of affairs to something a little less 'stupid', for want of a better word. Right now I have a DB class that deals with connection and escaping values etc, a parent db query class that deals with the common queries and methods, and all of the other classes (Thread, Upload, Session, Photo and ones thats aren't used Post, User etc ) are children of that. Do I make a big posts class that has the relevant extra attributes that I retrieve from the users (and potentially threads) table? Do I have separate classes that populate each of their relevant attributes with a single query? If so how do I do that? Because of the way my classes are written, based on what I was taught, my db update row method, or insert method both just take the attributes as an array and update all of that, if I have extra attributes from other db tables in each class then how do I rewrite those methods as obbiously updating automatically like that would result in errors? In short I think my understanding is limited right now and I'd like some pointers when it comes to the fundamentals of how to write more complex classes.

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  • Multiset container appears to stop sorting

    - by Sarah
    I would appreciate help debugging some strange behavior by a multiset container. Occasionally, the container appears to stop sorting. This is an infrequent error, apparent in only some simulations after a long time, and I'm short on ideas. (I'm an amateur programmer--suggestions of all kinds are welcome.) My container is a std::multiset that holds Event structs: typedef std::multiset< Event, std::less< Event > > EventPQ; with the Event structs sorted by their double time members: struct Event { public: explicit Event(double t) : time(t), eventID(), hostID(), s() {} Event(double t, int eid, int hid, int stype) : time(t), eventID( eid ), hostID( hid ), s(stype) {} bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } double time; ... }; The program iterates through periods of adding events with unordered times to EventPQ currentEvents and then pulling off events in order. Rarely, after some events have been added (with perfectly 'legal' times), events start getting executed out of order. What could make the events ever not get ordered properly? (Or what could mess up the iterator?) I have checked that all the added event times are legitimate (i.e., all exceed the current simulation time), and I have also confirmed that the error does not occur because two events happen to get scheduled for the same time. I'd love suggestions on how to work through this. The code for executing and adding events is below for the curious: double t = 0.0; double nextTimeStep = t + EPID_DELTA_T; EventPQ::iterator eventIter = currentEvents.begin(); while ( t < EPID_SIM_LENGTH ) { // Add some events to currentEvents while ( ( *eventIter ).time < nextTimeStep ) { Event thisEvent = *eventIter; t = thisEvent.time; executeEvent( thisEvent ); eventCtr++; currentEvents.erase( eventIter ); eventIter = currentEvents.begin(); } t = nextTimeStep; nextTimeStep += EPID_DELTA_T; } void Simulation::addEvent( double et, int eid, int hid, int s ) { assert( currentEvents.find( Event(et) ) == currentEvents.end() ); Event thisEvent( et, eid, hid, s ); currentEvents.insert( thisEvent ); }

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  • What alternatives do I have for source control and does GIT does that?

    - by RubberDuck
    I work as a freelancer programmer for some clients and also create apps for myself. When I work for myself, obviously I work alone. I generally don't work in a linear way. My big problems today are: I have a lot of apps that use the same classes I have developed; In the past, I put all these common classes on a directory outside all projects and included them on my apps using absolute paths, but this method sucks because by accident (if you forget) you may change a path or the disk and all projects are broken. Then I decided to copy those classes to my projects every time. Because the majority of these classes do not change frequently, I am relatively ok, but when they change, I am in hell; When I change one of these classes I have to propagate the changes to all other apps using copies of them. I have also tried to create frameworks but thanks to Apple, I cannot create frameworks for iOS and have to create libraries and bundles and create a nightmare of paths from one to the other and to the project to make that sh!t works. So, I am done with frameworks/libraries on Xcode until Xcode is a decent IDE. So, I see I need something better to manage my source code. What I need is this (I never used GIT on Xcode. I have read Apple docs but I still have these points): does git locally on Xcode allows me to deal with assets or just code? Can I have the equivalent of a "framework" (code + assets) managed by git locally? Can an entire xcodeproj be managed as a unity? I mean, Suppose I have a xcodeproj created and want GIT to manage it. How do I enable git on a project that was created without it and start designating files for management. (I have enabled git on Xcode's preferences, but all source control menu is grayed out). Is git the best option? Do I have another? Remember that my main condition is that the files should stay on the local computer. Please save me (I am a bit dramatic today). Thanks.

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  • How should I handle the case in which a username is already in use?

    - by idealmachine
    I'm a JavaScript programmer and new to PHP and MySQL (want to get into server-side coding). Because I'm trying to learn PHP by building a simple online game (more specifically, correspondence chess), I'm starting by implementing a simple user accounts system. Of course, user registration comes first. What are the best practices for: How I should handle the (likely) possibility that when a user tries to register, the username he has chosen is already in use, particularly when it comes to function return values?($result === true is rather ugly, and I'm not sure whether checking the MySQL error code is the best way to do it either) How to cleanly handle varying page titles?($gPageTitle = '...'; require_once 'bgsheader.php'; is also rather ugly) Anything else I'm doing wrong? In some ways, PHP is rather different from JavaScript... Here is a (rather large) excerpt of the code I have written so far. Note that this is a work in progress and is missing security checks that I will add as my next step. function addUser( $username, $password ) { global $gDB, $gPasswordSalt; $stmt = $gDB->prepare( 'INSERT INTO user(user_name, user_password, user_registration) VALUES(?, ?, NOW())' ); $stmt || trigger_error( 'Failed to prepare statement: ' . htmlspecialchars( $gDB->error ) ); $hashedPassword = hash_hmac( 'sha256', $password, $gPasswordSalt, true ); $stmt->bind_param( 'ss', $username, $hashedPassword ); if( $stmt->execute() ) { return true; } elseif( $stmt->errno == 1062) { return 'exists'; } else { trigger_error( 'Failed to execute statement: ' . htmlspecialchars( $stmt->error ) ); } } $username = $_REQUEST['username']; $password = $_REQUEST['password']; $result = addUser( $username, $password ); if( $result === true ) { $gPageTitle = 'Registration successful'; require_once 'bgsheader.php'; echo '<p>You have successfully registered as ' . htmlspecialchars( $username ) . ' on this site.</p>'; } elseif( $result == 'exists' ) { $gPageTitle = 'Username already taken'; require_once 'bgsheader.php'; echo '<p>Someone is already using the username you have chosen. Please try using another one instead.'; } else { trigger_error('This should never happen'); } require_once 'bgsfooter.php';

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  • c# video equivalent to image.fromstream? Or changing the scope of the following script to allow vide

    - by Daniel
    The following is a part of an upload class in a c# script. I'm a php programmer, I've never messed with c# much but I'm trying to learn. This upload script will not handle anything except images, I need to adapt this class to handle other types of media also, or rewrite it all together. If I'm correct, I realize that using (Image image = Image.FromStream(file.InputStream)) basically says that the scope of the following is Image, only an image can be used or the object is discarded? And also that the variable image is being created from an Image from the file stream, which I understand to be, like... the $_FILES array in php? I dunno, I don't really care about making thumbnails right now either way, so if this can be taken out and still process the upload I'm totally cool with that, I just haven't had any luck getting this thing to take anything but images, even when commenting out that whole part of the class... protected void Page_Load(object sender, EventArgs e) { string dir = Path.Combine(Request.PhysicalApplicationPath, "files"); if (Request.Files.Count == 0) { // No files were posted Response.StatusCode = 500; } else { try { // Only one file at a time is posted HttpPostedFile file = Request.Files[0]; // Size limit 100MB if (file.ContentLength > 102400000) { // File too large Response.StatusCode = 500; } else { string id = Request.QueryString["userId"]; string[] folders = userDir(id); foreach (string folder in folders) { dir = Path.Combine(dir, folder); if (!Directory.Exists(dir)) Directory.CreateDirectory(dir); } string path = Path.Combine(dir, String.Concat(Request.QueryString["batchId"], "_", file.FileName)); file.SaveAs(path); // Create thumbnail int dot = path.LastIndexOf('.'); string thumbpath = String.Concat(path.Substring(0, dot), "_thumb", path.Substring(dot)); using (Image image = Image.FromStream(file.InputStream)) { // Find the ratio that will create maximum height or width of 100px. double ratio = Math.Max(image.Width / 100.0, image.Height / 100.0); using (Image thumb = new Bitmap(image, new Size((int)Math.Round(image.Width / ratio), (int)Math.Round(image.Height / ratio)))) { using (Graphics graphic = Graphics.FromImage(thumb)) { // Make sure thumbnail is not crappy graphic.SmoothingMode = SmoothingMode.HighQuality; graphic.InterpolationMode = InterpolationMode.High; graphic.CompositingQuality = CompositingQuality.HighQuality; // JPEG ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders()[1]; // 90% quality EncoderParameters encode = new EncoderParameters(1); encode.Param[0] = new EncoderParameter(Encoder.Quality, 90L); // Resize graphic.DrawImage(image, new Rectangle(0, 0, thumb.Width, thumb.Height)); // Save thumb.Save(thumbpath, codec, encode); } } } // Success Response.StatusCode = 200; } } catch { // Something went wrong Response.StatusCode = 500; } } }

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  • Is valgrind crazy or is this is a genuine std map iterator memory leak?

    - by Alberto Toglia
    Well, I'm very new to Valgrind and memory leak profilers in general. And I must say it is a bit scary when you start using them cause you can't stop wondering how many leaks you might have left unsolved before! To the point, as I'm not an experienced in c++ programmer, I would like to check if this is certainly a memory leak or is it that Valgrind is doing a false positive? typedef std::vector<int> Vector; typedef std::vector<Vector> VectorVector; typedef std::map<std::string, Vector*> MapVector; typedef std::pair<std::string, Vector*> PairVector; typedef std::map<std::string, Vector*>::iterator IteratorVector; VectorVector vv; MapVector m1; MapVector m2; vv.push_back(Vector()); m1.insert(PairVector("one", &vv.back())); vv.push_back(Vector()); m2.insert(PairVector("two", &vv.back())); IteratorVector i = m1.find("one"); i->second->push_back(10); m2.insert(PairVector("one", i->second)); m2.clear(); m1.clear(); vv.clear(); Why is that? Shouldn't the clear command call the destructor of every object and every vector? Now after doing some tests I found different solutions to the leak: 1) Deleting the line i-second-push_back(10); 2) adding a delete i-second; after it's been used. 3) Deleting the second vv.push_back(Vector()); and m2.insert(PairVector("two", &vv.back())); statements. Using solution 2) makes Valgring print: 10 allocs, 11 frees Is that OK? As I'm not using new why should I delete? Thanks, for any help!

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  • Converting this code from ASP to PHP

    - by jethomas
    I'll admit I'm a novice programmer and really the only experience I have is in classic ASP. I'm looking for a way to convert this asp code to PHP. For a customer who only has access to a linux box but also as a learning tool for me. Thanks in advance for the help: Recordset and Function: Function pd(n, totalDigits) if totalDigits > len(n) then pd = String(totalDigits-len(n),"0") & n else pd = n end if End Function 'declare the variables Dim Connection Dim Recordset Dim SQL Dim SQLDate SQLDate = Year(Date)& "-" & pd(Month(Date()),2)& "-" & pd(Day(Date()),2) 'declare the SQL statement that will query the database SQL = "SELECT * FROM tblXYZ WHERE element_8 = 2 AND element_9 > '" & SQLDate &"'" 'create an instance of the ADO connection and recordset objects Set Connection = Server.CreateObject("ADODB.Connection") Set Recordset = Server.CreateObject("ADODB.Recordset") 'open the connection to the database Connection.Open "PROVIDER=MSDASQL;DRIVER={MySQL ODBC 5.1 Driver};SERVER=localhost;UID=xxxxx;PWD=xxxxx;database=xxxxx;Option=3;" 'Open the recordset object executing the SQL statement and return records Recordset.Open SQL,Connection Display page/loop: Dim counter counter = 0 While Not Recordset.EOF counter = counter + 1 response.write("<div><td width='200' valign='top' align='center'><a href='" & Recordset("element_6") & "' style='text-decoration: none;'><div id='ad_header'>" & Recordset("element_3") & "</div><div id='store_name' valign='bottom'>" & Recordset("element_5") & "</div><img id='photo-small-img' src='http://xyz.com/files/" & Recordset("element_7") & "' /><br /><div id='ad_details'>"& Recordset("element_4") & "</div></a></td></div>") Recordset.MoveNext If counter = 3 Then Response.Write("</tr><tr>") counter = 0 End If Wend

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  • Custom cell in list in Flash AS3

    - by Stian Flatby
    I am no expert in Flash, and I need some quick help here, without needing to learn everything from scratch. Short story, I have to make a list where each cell contains an image, two labels, and a button. List/Cell example: img - label - label - button img - label - label - button As a Java-programmer, I have tried to quicly learn the syntax and visualness of Flash and AS3, but with no luck so far. I have fairly understood the basics of movie clips etc. I saw a tutorial on how to add a list, and add some text to it. So I dragged in a list, and in the code went list.addItem({label:"hello"}); , and that worked ofc. So i thought if I double-clicked the MC of the list, i would get to tweak some things. In there I have been wandering around different halls of cell-renderers etc. I have now come to the point that I entered the CellRenderer_skinUp or something, and customized it to my liking. When this was done, I expected i could use list.addItem(); and get an empty "version" of my cell, with the img, labels and the button. But AS3 expects an input in addItem. From my object-oriented view, I am thinking that i have to create an object of the cell i have made, but i have no luck reaching it.. I tried to go var test:CellRenderer = list.listItem; list.addItem(test); ..But with no luck. This is just for funsies, but I really want to make this work, however not so much that I am willing to read up on ALOT of Flash and AS3. I felt that I was closing in on the prize, but the compiler expected a semicolon after the variable (list.addItem({test:something});). Note: If possible, I do NOT want this: list.addItem({image:"src",label:"text",label"text",button:"text"}); Well.. It actually is what I want, but I would really like to custom-draw everything. Does anyone get what I am trying to do, and has any answers for me? Am I approaching this the wrong way? I have searched the interwebs for custom list-cells, but with no luck. Please, any guiding here is appreciated! Sti

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  • When may I ask a question to fellow developers? (Rules before asking questions).

    - by Zwei Steinen
    I assigned a quite simple task to one junior developer today, and he kept pinging me EVERY 5 minutes for HOURS, asking STEP BY STEP, what to do. Whenever something went wrong, he simply copy&pasted the log and basically wrote, "An exception occurred. What should I do?" So I finally had to tell him, "If you want to be a developer, please start thinking a little bit. Read the error message. That's what they are for!". I also however, tell junior developers to ask questions before spending too much time trying to solve it themselves. This might sound contradictory, but I feel there is some kind of an implicit rule that distinguishes questions that should be asked fairly quickly and that should not (and I try to follow those rules when I ask questions..) So my question is, do you have any rules that you follow, or expect others to follow on asking questions? If so, what are they? Let me start with my own. If you have struggled for more than 90 min, you may ask that question (exceptions exists). If you haven't struggled for more than 15 min, you may not ask that question (if you are sure that the answer can not be found within 15 min, this rule does not have to apply). If it is completely out of your domain and you do not plan to learn that domain, you may ask that question after 15 min (e.g. if I am a java programmer and need to back up the DB, I may ask the DBA what procedure to follow after googling for 15 min). If it is a "local" question, whose answer is difficult to derive or for which resources is difficult to get (e.g. asking an colleague "what method xxx does" etc.), you may ask that question after 15 min. If the answer for it is difficult to derive, and you know that the other person knows the answer, you may ask the question after 15 min (e.g. asking a hibernate expert "What do I need to change else to make this work?". If the process to derive the answer is interesting and is a good learning opportunity, you may ask for hints but you may not ask for answers! What are your rules?

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  • Showing div based on filled form field

    - by Fabio
    I have this script where I use a slider to show some elements of a form. So far so good. The way I'm doing it is by having a slider (can't use a multistep form since it uses a plugin not allowing multistep forms, plus some graphic behaviors) and a button that goes to the next slider. So now I need that button (not part of the form) to show only if a certain field is filled. I tried teh following, but it's not working, I assume some error but can't figure what. My code is as follows: $('#clientname').change(function() { var clientVal = $("input").val() == ''; $(".next").hide(); if ($('#clientname').val() != '').show(); else $('.next').hide(); }); and the html as follows: <div class="b40-right"> <h3>The Basics</h3> <div class="label"> Your Name (required)</div> <div class="inputes"> <span class="wpcf7-form-control-wrap your-name"><input id="clientname" type="text" name="your-name" value="" class="wpcf7-form-control wpcf7-text wpcf7-validates-as-required" size="40" /></span> </div> <div class="label">Your Email (required)</div> <div class="inputes"> <span class="wpcf7-form-control-wrap your-email"><input type="text" name="your-email" value="" class="wpcf7-form-control wpcf7-text wpcf7-email wpcf7-validates-as-required wpcf7-validates-as-email" size="40" /></span> </div> <div class="label">Type of Business</div> <div class="inputes"> <span class="wpcf7-form-control-wrap type-of-business"><textarea name="type-of-business" class="wpcf7-form-control wpcf7-textarea" cols="40" rows="10"></textarea></span> </div> </div> <a class="next" href="javascript:stepcarousel.stepBy('mygallery2', 1)"><img id="nextbut1" src="<?php bloginfo('template_directory'); ?>/images/next.png" alt="" /></a> any help on what am I doing wrong? Is there a better approach/solution? (I'm not a programmer as you may figure) Thank you in advance!

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