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• correct way to store an exception in a variable

  - by Evan Teran

  I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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• regex pattern to match only strings that don't contain spaces PHP

  - by Jamex

  Hi, I want to match the word/pattern that is contained in the variable, but only match against the words that don't have white spaces. Please give suggestions. $var = 'look'; $array = ('look', 'greatlook', 'lookgreat', 'look great', 'badlook', 'look bad', 'look ', ' look'); matches words: look, greatlook, lookgreat, badlook non matches: look great, bad look, look (trailing space(s)), (space(s)) look. The syntax of the below functions are OK, but it matches everything $match = preg_grep ("/$var/", $array); $match = preg_grep ("/^$var/", $array); (match words with 'look' at the start) but when I include the [^\s], it gives an error $match = preg_grep ("/$var[^\s]/", $array); Parse error: syntax error, unexpected '^', expecting T_STRING or T_VARIABLE TIA

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• Functional languages & support for memoization

  - by Joel

  Do any of the current crop of popular functional languages have good support for memoization & if I was to pick one on the strength of its memoisation which would you recommend & why? Update: I'm looking to optimise a directed graph (where nodes could be functions or data). When a node in the graph is updated I would like the values of other nodes to be recalculated only if they depend the node that changed. Update2: require free or open-source language/runtime.

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• How to create a string array in matlab?

  - by aduric

  I would like to pass a vector of strings from C++ to matlab. I have tried using the functions available such as mxCreateCharMatrixFromStrings but it doesn't give me the correct behavior. So, I have something like this: void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { vector<string> stringVector; stringVector.push_back("string 1"); stringVector.push_back("string 2"); //etc... The problem is how do I get this vector to the matlab environment? plhs[0] = ??? My goal is to be able to run: >> [strings] = MyFunc(...) >> strings(1) = 'string 1'

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• Must a Language that Implements Monads be Statically Typed?

  - by Morgan Cheng

  I am learning functional programming style. From this link http://channel9.msdn.com/shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads/, Brian Beckman gave a brilliant introduction about Monad. He mentioned that Monad is about composition of functions so as to address complexity. A Monad includes a unit function that transfers type T to an amplified type M(T); and a Bind function that, given function from T to M(U), transforms type M(T) to another type M(U). (U can be T, but is not necessarily). In my understanding, the language implementing monad should be type-checked statically. Otherwise, type errors cannot be found during compilation and "Complexity" is not controlled. Is my understanding correct?

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• use callback function to report stack backtrace

  - by user353394

  Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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• Issues rendering image in flash via Context.Response.Write C# asp.

  - by Justin

  I am having an issue rendering images in flash via a character array. I am sending it from a webhandler via Context.Response.Write as a Base64CharacterArray. It functions 100% properly in a windows environment, however when using a Mac the image data is not retrieved correctly causing the image to appear incorrectly. It does not affect the data,however as it is rendered properly in a player which accesses the data via a webservice. I am at the end of my rope on this one. Anything will help. You can find an example at the following url http://www.discoverirelandtoday.com/photoalbum/Public/Main.aspx Thanks

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• Why my print current date time (C language) gives different answer

  - by vodkhang

  I want to get the current date (day, mon and year). I found out there are some functions in C to do that like ctime (get the string of time), localtime and gmtime. I tried with following code but the output are different. I get this output: The date and time is Tue Apr 20 2010 (which is correct) The year is : 110 The year is : 110. Does anybody know why? int main(int argc, char** argv) { time_t now; if((now = time(NULL)) == (time_t)-1) { puts("Failure in getting time"); } else { printf("The date and time is: %s\n", ctime(&now)); printf("The year is: %ld\n", localtime(&now)->tm_year); printf("The year is: %ld\n", gmtime(&now)->tm_year); } getchar(); }

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• Type patterns in Haskell

  - by finnsson

  I'm trying to compile a simple example of generic classes / type patterns (see http://www.haskell.org/ghc/docs/latest/html/users_guide/generic-classes.html) in Haskell but it won't compile. Any ideas about what's wrong with the code would be helpful. According to the documentation there should be a module Generics with the data types Unit, :*:, and :+: but ghc (6.12.1) complaints about Not in scope: data constructor 'Unit' etc. It seems like there's a package instant-generics with the data types :*:, :+: and U but when I import that module (instead of Generics) I get the error Illegal type pattern in the generic bindings {myPrint _ = ""} The complete source code is import Generics.Instant class MyPrint a where myPrint :: a -> String myPrint {| U |} _ = "" myPrint {| a :*: b |} (x :*: y) = "" (show x) ++ ":*:" ++ (show y) myPrint {| a :+: b |} _ = "" data Foo = Foo String instance MyPrint a => MyPrint a main = myPrint $ Foo "hi" and I compile it using ghc --make Foo.hs -fglasgow-exts -XGenerics -XUndecidableInstances P.S. The module Generics export no data types, only the functions: canDoGenerics mkGenericRhs mkTyConGenericBinds validGenericInstanceType validGenericMethodType

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• Caching result of setUp() using Python unittest

  - by dbr

  I currently have a unittest.TestCase that looks like.. class test_appletrailer(unittest.TestCase): def setup(self): self.all_trailers = Trailers(res = "720", verbose = True) def test_has_trailers(self): self.failUnless(len(self.all_trailers) > 1) # ..more tests.. This works fine, but the Trailers() call takes about 2 seconds to run.. Given that setUp() is called before each test is run, the tests now take almost 10 seconds to run (with only 3 test functions) What is the correct way of caching the self.all_trailers variable between tests? Removing the setUp function, and doing.. class test_appletrailer(unittest.TestCase): all_trailers = Trailers(res = "720", verbose = True) ..works, but then it claims "Ran 3 tests in 0.000s" which is incorrect.. The only other way I could think of is to have a cache_trailers global variable (which works correctly, but is rather horrible): cache_trailers = None class test_appletrailer(unittest.TestCase): def setUp(self): global cache_trailers if cache_trailers is None: cache_trailers = self.all_trailers = all_trailers = Trailers(res = "720", verbose = True) else: self.all_trailers = cache_trailers

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• Setting the Cursor Position in a Win32 Console Application

  - by Jim Fell

  How can I set the cursor position in a Win32 Console application? Preferably, I would like to avoid making a handle and using the Windows Console Functions. (I spent all morning running down that dark alley; it creates more problems than it solves.) I seem to recall doing this relatively simply when I was in college using stdio, but I can't find any examples of how to do it now. Any thoughts or suggestions would be greatly appreciated. Thanks.

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• Maintaining the query string in ASP.Net MVC

  - by Mantorok

  Hi all Just beginning my journey in ASP.Net MVC and I have a query about something before I dig myself in too deep. I have a table, which is paged, and I have 2 controls above the table: Dropdown that defines order of the results and apply button next to it Textbox that defines a filter and apply button next to it What I need to achieve is that if the user changes the order or adds a filter I fire of an AJAX call to my action like such: /Membership/Users?sort=value&filter=value&page=pagenumber. So my controller action is: // GET Membership/Users?sort=&filter=&page= public ActionResult Users(string sort, string filter, string page) So I have 3 questions: Is this the correct approach? What would be the best way to ensure that the query string is maintained, bearing in mind that the action will nearly always be called by Jquery/Ajax functions? If I wanted to link directly to this action passing the arguments would I need to hard-code the querystring? Thanks

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• How can I upload a file to a Sharepoint Document Library using Silverlight and client web-services?

  - by pclem12

  Most of the solutions I've come across for Sharepoint doc library uploads use the HTTP "PUT" method, but I'm having trouble finding a way to do this in Silverlight because it has restrictions on the HTTP Methods. I visited this http://msdn.microsoft.com/en-us/library/dd920295(VS.95).aspx to see how to allow PUT in my code, but I can't find how that helps you use an HTTP "PUT". I am using client web-services, so that limits some of the Sharepoint functions available. That leaves me with these questions: Can I do an http PUT in Silverlight? If I can't or there is another better way to upload a file, what is it? Thanks

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• Getters and Setters: Code smell, Necessary Evil, or Can't Live Without Them [closed]

  - by Avery Payne

  Possible Duplicate: Allen Holub wrote “You should never use get/set functions”, is he correct? Is there a good, no, a very good reason, to go through all the trouble of using getters and setters for object-oriented languages? What's wrong with just using a direct reference to a property or method? Is there some kind of "semantical coverup" that people don't want to talk about in polite company? Was I just too tired and fell asleep when someone walked out and said "Thou Shalt Write Copious Amounts of Code to Obtain Getters and Setters"? Follow-up after a year: It seems to be a common occurrence with Java, less so with Python. I'm beginning to wonder if this is more of a cultural phenomena (related to the limitations of the language) rather than "sage advice". The -1 question score is complete for-the-lulz as far as I am concerned. It's interesting that there are specific questions that are downvoted, not because they are "bad questions", but rather, because they hit someone's raw nerve.

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• Setting creation or change timestamps

  - by Thanatos

  Using utimes, futimes, futimens, etc., it is possible to set the access and modification timestamps on a file. Is there a function to set change timestamps? (I understand the cyclic nature of wanting to change the change timestamp, but think archiving software - it would be nice to restore a file exactly as it was.) Are there any functions at all for creation timestamps? (I realize that ext2 does not support this, but I was wondering if Linux did, for those filesystems that do support it.) If it's not possible, what is the reasoning behind it not being so?

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• Generating random numbers in C

  - by moonstruckhorrors

  While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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• Why use event listeners over function calls?

  - by Organiccat

  I've been studying event listeners lately and I think I've finally gotten them down. Basically, they are functions that are called on another object's method. My question is, why create an event listener when calling the function will work just fine? Example, I want to call player.display_health(), and when this is fired, the method player.get_health() should be fired and stored so that display_health() has access to it. Why should I use an event listener over simply calling the function? Even if display_health() were in another object, this still doesn't appear to be a problem to me. If you have another example that fits the usage better, please let me know. Perhaps particular languages don't benefit from it as much? (Javascript, PHP, ASP?)

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• Switching Javascript Function states

  - by webzide

  Dear experts, I would like to implement a API of Javascript that sort of resemble a light switch. For instance, there are two buttons on the actual HTML page act as the UI. Both of the buttons have event handlers that invokes a different function. Each function have codes that act like a state, for instance. button1.onclick=function (){ $("div").click( //code effects 2 ) } button2.onclick=function (){ $("div").click( //Code effects 2 ) } I the code works fine on the surface but the 2 state functions overlap. the effects is going to take place for the rest of the way until the next reload of the document. Basically what I want to achieve is that when 1 button is clicked, it will switch "OFF" the state of function invoked by the other button and vice versa. Thus, the effects achieved are unique are not overlapped. Is there anyway to achieve this or could any experts point me to the right direction. Thanks in advance.

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• Is it bad practice to use python's getattr extensively?

  - by Wilduck

  I'm creating a shell-like environment. My original method of handleing user input was to use a dictionary mapping commands (strings) to methods of various classes, making use of the fact that functions are first class objects in python. For flexibility's sake (mostly for parsing commands), I'm thinking of changing my setup such that I'm using getattr(command), to grab the method I need and then passing arguments to it at the end of my parser. Another advantage of this approach is not having to update my (currently statically implemented) command dictionary every time I add a new method/command. My question is, will I be taking a hit to the efficiency of my shell? Does it matter how many methods/commands I have? I'm currently looking at 30 some commands, which could eventually double.

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• car and cdr in Scheme are driving me crazy ...

  - by kristian Roger

  Hi Im facing a problem with the car and cdr functions for example: first I defined a list called it x (define x (a (bc) d ( (ef) g ) )) so x now is equal to (a (bc) d ( (ef) g ) ) now for example I need to get the g from this list using only car and cdr (!! noshortcuts as caddr cddr !!) the correct answer is: (car(cdr(car(cdr(cdr(cdr x)))))) BUT how ? :-( I work according to the rules (the car gives the head of list and cdr gives the tail) and instead of getting the answer above I keep reaching wrong answers. Can any one help me in understanding this ... give me step or a way to solve it step by step Thanks in advance. I'm really sick of Scheme.

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• Is it possible to register a user and submit a comment with one form with Wordpress?

  - by zack

  Is it possible to do both registering for an account and submit a comment at the same time? I want the user to be able to do this all on one page to ecourage the registration rather than be discouraged about typing something, not realizing they had to be registered and thus having to leave the page. I think that this could be done by adding register user action to the submit comment action, but not sure how to do it with the prebuilt wordpress add_action or do_action functions. Has anyone tried this, or know of any plug-ins that do this already? I searched but couldn't find anything helpful. Thanks.

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• Group MySQL Data into Arbitrarily Sized Time Buckets

  - by Eric J.

  How do I count the number of records in a MySQL table based on a timestamp column per unit of time where the unit of time is arbitrary? Specifically, I want to count how many record's timestamps fell into 15 minute buckets during a given interval. I understand how to do this in buckets of 1 second, 1 minute, 1 hour, 1 day etc. using MySQL date functions, e.g. SELECT YEAR(datefield) Y, MONTH(datefield) M, DAY(datefield) D, COUNT(*) Cnt FROM mytable GROUP BY YEAR(datefield), MONTH(datefield), DAY(datefield) but how can I group by 15 minute buckets?

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• What does static linking against a library actually do?

  - by Salgar

  Say I had a library called libfoo which contained a class, a few static variables, possibly something with 'C' linkage, and a few other functions. Now I have a main program which looks like this: int main() { return 5+5; } When I compile and link this, I link against libfoo. Will this have any effect? Will my executable increase in size? If so, why? Do the static variables or their addresses get copied into my executable? Apologies if there is a similar question to this or if I'm being particularly stupid in any way.

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• Is there a language designed for code golf?

  - by J S

  I am not really a fan of code golf, but I have to wonder, is there an esoteric language designed for it? I mean a language with following properties: Common programs may be expressed in very short amount of characters It uses ASCII character set effectively (for example, common operators are not identifiers, so they don't have to be separated by whitespace, character usage is distributed more or less evenly because we cannot use Huffman coding and so on) Except the terse syntax, it should have very expressible and clean semantics (like, let's say, Python or Scheme); it shouldn't be difficult to program in It doesn't need features for large scale programs, such as OOP, but it definitely should allow custom functions and data structures It should have a large standard library, identifiers in this library should be as short as possible Maybe it should be called CG? Languages that can be a source of inspiration are Forth, APL and Joy.

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• What are Class methods in Python for?

  - by Dave Webb

  I'm teaching myself Python and my most recent lesson was that Python is not Java, and so I've just spent a while turning all my Class methods into functions. I now realise that I don't need to use Class methods for what I would done with static methods in Java, but now I'm not sure when I would use them. All the advice I can find about Python Class methods is along the lines of newbies like me should steer clear of them, and the standard documentation is at its most opaque when discussing them. Does anyone have a good example of using a Class method in Python or at least can someone tell me when Class methods can be sensibly used?

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