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  • How do you use stl's functions like for_each?

    - by thomas-gies
    I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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  • Adding functions to Java class libraries

    - by Eric
    I'm using a Java class library that is in many ways incomplete: there are many classes that I feel ought to have additional member functions built in. However, I am unsure of the best practice of adding these member functions. Lets call the insufficient base class A. class A { public A(/*long arbitrary arguments*/) { //... } public A(/*long even more arbitrary arguments*/) { //... } public int func() { return 1; } } Ideally, I would like to add a function to A. However, I can't do that. My choice is between: class B extends A { //Implement ALL of A's constructors here public int reallyUsefulFunction() { return func()+1; } } and class AddedFuncs { public int reallyUsefulFunction(A a) { return a.func()+1; } } The way I see it, they both have advantages and disadvantages. The first choice gives a cleaner syntax than the second, and is more logical, but has problems: Let's say I have a third class, C, within the class library. class C { public A func() { return new A(/*...*/); } } As I see it, there is no easy way of doing this: C c; int useful = c.func().reallyUsefulFunction(); as the type returned by C.func() is an A, not a B, and you can't down-cast. So what is the best way of adding a member function to a read-only library class?

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  • Passing unknown amounts of variables using through a string string and eval and multiple functions a

    - by user300797
    I'm not sure how best to describe this problem... In short, I want to use object literal to allow me to pass a random amount of variables in any order to a function. Whilst this is not big deal in theory, in my code, this object literal is passed to a second function call on_change. on_change works comparing an element inner HTML to a string. if it is the same, it sets a time out of to call the function again (this is sort of/almost recursive, but the function dose actually get to end before it is called again). if the elements inner HTML is different from the string, then the third parameter is executed. this will either be a function or a string. either way it will execute. I have tested this function plenty and used it for a while now. how ever, it cannot seem to get the object literal to flow through the function calls... var params = { xpos:'false'}; on_change('window_3_cont_buffer','',' if(Window_manager.windows[3].window_cont_buffer.getElementsByTagName(\'content\')[0].getElementsByTagName(\'p\')[0].innerHTML == \'ERROR\'){ alert(Window_manager.windows[3].window_cont_buffer.getElementsByTagName(\'content\')[0].getElementsByTagName(\'p\')[1].innerHTML); return false; } else { Window_manager.windows[3].load_xml(\'location/view.php?location_ID=3\', \'\', ' + params + ' ); } '); I call this as part of the form submission. after this line, I then call a function to load some content via ajax, which works fine and will trigger the code from the on_change function. I have tested load_xml function it is able to call alert(param.xpos) and get the correct response. I can even added in a check for being undefined so that rest of the times I cam load_xml I don't get swamped with alerts. The load_xml function first set up the on_change function, then calls the function to load the content to a hidden div. Once the AJAX request has updated that DIV, the on_change function should now call the parse_xml function. This pulls out the information from the xml file. How ever... The idea of this object literal param is that it can tell this parse_xml function to ignore certain things. on_change("window_" + this.id + "_cont_buffer", "", "Window_manager.windows[" + this.id + "].parse_xml('" + param + "')"); this is part of load_xml. it works perfectly fine, even with the param bit in there. except, parse_xml dose not seem to be able to use that parameter. I have been able to get it to a point where parse_xml can alert(param) and give [object object] which I would of thought meant that the object litteral had been passed through, but when I try and call alert(param.xpos) I get undefined. I know this is a pig of a problem, and I could get around it by just having the function take a zillion boolean parameters, but its just not practical or elegant. I'm sure you will need to ask me plenty more questions before I can solve this. I will post more complete code, I just cut it down to what is actually going on. Thanks

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  • Calling methods or functions with Jquery

    - by Ross
    So I can call a php page using jquery $.ajax({ type: "GET", url: "refresh_news_image.php", data: "name=" + name, success: function(html) { alert(html) $('div.imageHolder').html(html); } }); However this getting a bit messy, I have a few .php files that only really preform very simple tasks. If I want to call a method $images-refresh_image(); is this possible. Failing that I could just create a big file with lots of functions in it? Thanks, Ross

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  • self join- how to use the aggregate functions

    - by Ranjana
    self join- how to use the aggregate functions select a.tablename, b.TableName,b.UserName from Employee a inner join Employee b on a.ColumnValue=b.ColumnValue and and a.TableName <> b.TableName and a.UserName=b.UserName and also to check whether the same user has count of records i.e Employee a = count of records of Employee b. how to add count function over here

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  • Overload Anonymous Functions

    - by Nissan Fan
    Still wrapping my head around Delegates and I'm curious: Is it possible to overload anonymous functions? Such that: delegate void Output(string x, int y); Supports: Output show = (x, y) => Console.WriteLine("{0}: {1}", x.ToString(), y.ToString()); And: delegate void Output(string x, string y); Allowing: show( "ABC", "EFG" ); And: show( "ABC", 123 );

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  • user generated / user specific functions

    - by pedalpete
    I'm looking for the most elegant and secure method to do the following. I have a calendar, and groups of users. Users can add events to specific days on the calendar, and specify how long each event lasts for. I've had a few requests from users to add the ability for them to define that events of a specific length include a break, of a certain amount of time, or require that a specific amount of time be left between events. For example, if event is 2 hours, include a 20min break. for each event, require 30 minutes before start of next event. The same group that has asked for an event of 2 hours to include a 20 min break, could also require that an event 3 hours include a 30 minute break. In the end, what the users are trying to get is an elapsed time excluding breaks calculated for them. Currently I provide them a total elapsed time, but they are looking for a running time. However, each of these requests is different for each group. Where one group may want a 30 minute break during a 2 hour event, and another may want only 10 minutes for each 3 hour event. I was kinda thinking I could write the functions into a php file per group, and then include that file and do the calculations via php and then return a calculated total to the user, but something about that doesn't sit right with me. Another option is to output the groups functions to javascript, and have it run client-side, as I'm already returning the duration of the event, but where the user is part of more than one group with different rules, this seems like it could get rather messy. I currently store the start and end time in the database, but no 'durations', and I don't think I should be storing the calculated totals in the db, because if a group decides to change their calculations, I'd need to change it throughout the db. Is there a better way of doing this? I would just store the variables in mysql, but I don't see how I can then say to mysql to calculate based on those variables. I'm REALLY lost here. Any suggestions? I'm hoping somebody has done something similar and can provide some insight into the best direction. If it helps, my table contains eventid, user, group, startDate, startTime, endDate, endTime, type The json for the event which I return to the user is {"eventid":"'.$eventId.'", "user":"'.$userId.'","group":"'.$groupId.'","type":"'.$type.'","startDate":".$startDate.'","startTime":"'.$startTime.'","endDate":"'.$endDate.'","endTime":"'.$endTime.'","durationLength":"'.$duration.'", "durationHrs":"'.$durationHrs.'"} where for example, duration length is 2.5 and duration hours is 2:30.

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  • JavaScript Collection of one-line Useful Functions

    - by Wilq32
    This is a question to put as many interesting and useful JavaScript functions written in one line as we can. I made this question because I'm curious how many people around like the art of one-Line programming in JavaScript, and I want to see their progress in action. Put variations of each code inside comments.

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  • Using multiple aggregate functions in an algebraic expression in (ANSI) SQL statement

    - by morpheous
    I have the following aggregate functions (AGG FUNCs): foo(), foobar(), fredstats(), barneystats(). I want to know if I can use multiple AGG FUNCs in an algebraic expression. This may seem a strange/simplistic question for seasoned SQL developers - however, the but the reason I ask is that so far, all AGG FUNCs examples I have seen are of the simplistic variety e.g. max(salary) < 100, rather than using the AGG FUNCs in an expression which involves using multiple AGG FUNCs in an expression (like agg_func1() agg_func2()). The information below should help clarify further. Given tables with the following schemas: CREATE TABLE item (id int, length float, weight float); CREATE TABLE item_info (item_id, name varchar(32)); # Is it legal (ANSI) SQL to write queries of this format ? SELECT id, name, foo, foobar, fredstats FROM A, B (SELECT id, foo(123) as foo, foobar('red') as foobar, fredstats('weight') as fredstats FROM item GROUP BY id HAVING [ALGEBRAIC EXPRESSION] ORDER BY id AS A), item_info AS B WHERE item.id = B.id Where: ALGEBRAIC EXPRESSION is the type of expression that can be used in a WHERE clause - for example: ((foo(x) < foobar(y)) AND foobar(y) IN (1,2,3)) OR (fredstats(x) <> 0)) I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible. Assuming it is legal to include AGG FUNCS in the way I have done above, I'd like to know: Is there a more efficient way to write the above query ? Is there any way I can speed up the query in terms of a judicious choice of indexes on the tables item and item_info ? Is there a performance hit of using AGG FUNCs in an algebraic expression like I am (i.e. an expression involving the output of aggregate functions rather than constants? Can the expression also include 'scaled' AGG FUNC? (for example: 2*foo(123) < -3*foobar(456) ) - will scaling (i.e. multiplying an AGG FUNC by a number have an effect on performance?) How can I write the query above using INNER JOINS instead?

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  • How to call JQuery functions

    - by Mohammad
    Hello, I was wondering about the different ways of using a JQuery function on a variable like I know this one $.DoThis(variable); but is there a way to call it at the end like normal Javascript functions variable.$.DoThis(); haha I know this sounds stupid but I need to ask somewhere. Thanks!

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  • Static Variables in Overloaded Functions

    - by BSchlinker
    I have a function which does the following: When the function is called and passed a true bool value, it sets a static bool value to true When the function is called and passed a string, if the static bool value is set to true, it will do something with that string Here is my concern -- will a static variable remain the same between two overloaded functions? If not, I can simply create a separate function designed to keep track of the bool value, but I try to keep things simple.

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  • How to start a Python script several functions in

    - by chrissygormley
    Hello, I have a Python script and I want to call it several functions down the script. Example code below: class Name(): def __init__(self): self.name = 'John' self.address = 'Place' self.age = '100' def printName(self): print self.name def printAddress(self): print self.address def printAge(self): print self.age if __name__ == '__main__': Person = Name() Person.printName() Person.printAddress() Person.printage() I execute this code by entering ./name.py. How could I exectute this code from the function printAddress() down the the end of the script? Thanks

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  • Calling cdecl Functions That Have Different Number of Arguments

    - by KlaxSmashing
    I have functions that I wish to call based on some input. Each function has different number of arguments. In other words, if (strcmp(str, "funcA") == 0) funcA(a, b, c); else if (strcmp(str, "funcB") == 0) funcB(d); else if (strcmp(str, "funcC") == 0) funcC(f, g); This is a bit bulky and hard to maintain. Ideally, these are variadic functions (e.g., printf-style) and can use varargs. But they are not. So exploiting the cdecl calling convention, I am stuffing the stack via a struct full of parameters. I'm wondering if there's a better way to do it. Note that this is strictly for in-house (e.g., simple tools, unit tests, etc.) and will not be used for any production code that might be subjected to malicious attacks. Example: #include <stdio.h> typedef struct __params { unsigned char* a; unsigned char* b; unsigned char* c; } params; int funcA(int a, int b) { printf("a = %d, b = %d\n", a, b); return a; } int funcB(int a, int b, const char* c) { printf("a = %d, b = %d, c = %s\n", a, b, c); return b; } int funcC(int* a) { printf("a = %d\n", *a); *a *= 2; return 0; } typedef int (*f)(params); int main(int argc, char**argv) { int val; int tmp; params myParams; f myFuncA = (f)funcA; f myFuncB = (f)funcB; f myFuncC = (f)funcC; myParams.a = (unsigned char*)100; myParams.b = (unsigned char*)200; val = myFuncA(myParams); printf("val = %d\n", val); myParams.c = (unsigned char*)"This is a test"; val = myFuncB(myParams); printf("val = %d\n", val); tmp = 300; myParams.a = (unsigned char*)&tmp; val = myFuncC(myParams); printf("a = %d, val = %d\n", tmp, val); return 0; } Output: gcc -o func func.c ./func a = 100, b = 200 val = 100 a = 100, b = 200, c = This is a test val = 200 a = 300 a = 600, val = 0

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  • C question on functions

    - by benjamin button
    some times i see that functions are defined as below: read_dir(dir) char *dir; { DIR * dirp; struct dirent *d; /* open directory */ dirp = opendir(dir); ......... so on here what is the importance of the statement char *dir; what is the intension behind declaring the pointer soon after the function name and then starting the function body.

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  • c++ inline functions

    - by user69514
    i'm confused about how to do inline functions in C++.... lets say this function. how would it be turned to an inline function int maximum( int x, int y, int z ) { int max = x; if ( y > max ) max = y; if ( z > max ) max = z; return max; }

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  • Sikuli List of Functions & Operators

    - by PPTim
    Hello, I've just discovered Sikuli, and would like to see a comprehensive functions list without digging through the online-examples and demos. Has anyone found such a list? Furthermore, apparently Sikuli supports more complex loops and function calls as well, and seems to be based in Python(!!). Examples would be great. Thanks.

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  • Python - output from functions?

    - by Seafoid
    Hi I have a very rudimentary question. Assume I call a function, e.g., def foo(): x = 'hello world' How do I get the function to return x in such a way that I can use it as the input for another function or use the variable within the body of a program? When I use return and call the variable within another functions I get a NameError. Thanks, S :-)

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  • Jquery with call back functions

    - by pplegend
    Hi, i have one problem with the Jquery callback functions, here is the link: http://saveenergy.metropolia.fi/views/pihkapuisto/ as you can see, the first page works fine. but all the others are not fine. they always right side and the size is too small. anyone knows how to change the position and size, make it looks like the first one? thanks

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