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  • Shall I optimize or let compiler to do that?

    - by Knowing me knowing you
    What is the preferred method of writing loops according to efficiency: Way a) /*here I'm hoping that compiler will optimize this code and won't be calling size every time it iterates through this loop*/ for (unsigned i = firstString.size(); i < anotherString.size(), ++i) { //do something } or maybe should I do it this way: Way b) unsigned first = firstString.size(); unsigned second = anotherString.size(); and now I can write: for (unsigned i = first; i < second, ++i) { //do something } the second way seems to me like worse option for two reasons: scope polluting and verbosity but it has the advantage of being sure that size() will be invoked once for each object. Looking forward to your answers.

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  • Difference between local and instance variables in ruby

    - by fflyer05
    I am working on a script that creates several fairly complex nested hash datastructures and then iterates through them conditionally creating database records. This is a standalone script using active record. After several minutes of running I noticed a significant lag in server responsiveness and discovered that the script, while being set to be nice +19, was enjoying a steady %85 - %90 total server memory. In this case I am using instance variables simply for readability. It helps knowing what is going to be re-used outside of the loop vs. what won't. Is there a reason to not use instance variables when they are not needed? Are there differences in memory allocation and management between local and instance variables? Would it help setting @variable = nil when its no longer needed?

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  • JQuery get height of each previous element

    - by Jk_
    I'm trying to find a good solution to get the height of all the element above my target. So loop the prev() function ! Any ideas on how I could deal with that ? <div> <div style="height:50px;width:100%"></div> <div style="height:12px;width:100%"></div> <div style="height:23px;width:100%"></div> <div style="height:56px;width:100%"></div> <div id="#mytarget"><p>HERE</p></div> </div> $('#mytarget').prev().each(function() { alert($(this).outerHeight()); }); and it will fires ["56","23","12","50"].

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  • dabbledb + iPhone

    - by user193545
    I have been using DabbbleDB online database for storing/retrieving values for one of my iPhone applications. I am using their JSON response for retrieving the records. The problem that I am facing is that if there are a large number of records in the database, it takes a long time to get the response from the server and then to parse the JSON response. Instead I would like to to get a set of records at a time and run a loop to fetch all the records in background. I do not know whether we can query for a set of records at a time from online databases like DabbleDB. Anybody having an idea, please help.

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  • How to do something after effect animation ends in Flex?

    - by Chobicus
    I'm a beginner in Flex so there must be more elegant way of doing this. //move effect private var m:Move = new Move(); //this function creates labels with some text and starts move effect on them public function moveText(i:int):void { var myLabel:Label = new Label(); myLabel.text = "some text"; m.target = myLabel; ... m.play(); } Method moveText is called in a loop so I guess that labels don't get "garbage collected". What I want to do is to remove Labels created in moveText method after play animation ends. Another way of doing this is maybe creating some kind of "pool" of labels which I would use to move arround text. I don't know how would I return labels in to "pool". The question is how to do something after effect animation ends?

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  • Birthday effect - clarification needed plz.

    - by Mark
    Please help interpret the Birthday effect as described in Wikipedia: A birthday attack works as follows: 1) Pick any message m and compute h(m). 2) Update list L. Check if h(m) is in the list L. 3) if (h(m),m) is already in L, a colliding message pair has been found. else save the pair (h(m),m) in the list L and go back to step 1. From the birthday paradox we know that we can expect to find a matching entry, after performing about 2^(n/2) hash evaluations. Does the above mean 2^(n/2) iterations through the above entire loop (i.e. 2^(n/2) returns to step 1), OR does it mean 2^(n/2) comparisons to individual items already in L.

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  • How to initialize std::vector from C-style array?

    - by dehmann
    What is the cheapest way to initialize a std::vector from a C-style array? Example: In the following class, I have a vector, but due to outside restrictions, the data will be passed in as C-style array: class Foo { std::vector<double> w_; public: void set_data(double* w, int len){ // how to cheaply initialize the std::vector? } Obviously, I can call w_.resize() and then loop over the elements, or call std::copy(). Are there any better methods?

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  • Implementing an iterator over binary tree using C++ 11

    - by user1459339
    I would like to create an iterator over the binary tree so as to be able to use range-based for loop. I understand I ought to implement the begin() and end() function first. Begin should probably point to the root. According to the specification, however, the end() functions returns "the element following the last valid element". Which element (node) is that? Would it not be illegal to point to some "invalid" place? The other thing is the operator++. What is the best way to return "next" element in tree? I just need some advice to begin with this programming.

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  • Ojective C Class or struct?

    - by Scott Pendleton
    I have a class Song with properties Title, Key, Artist, etc. There are no methods. I loop through a database of song information and create a Song object for each, populating the properties, and then store the Song objects in an NSArray. Then I thought, why not just have a struct Song with all those same properties instead of a class Song. Doing so would eliminate the class files, the #import Song line in the using class's .m file, and the need to alloc, init, release. On the other hand, I'd have to put the struct definition in every class that might need it. (Unless there's some globally accessible location -- is there?) Also, can a struct be stored in an NSArray?

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  • How to get the set events of a control?

    - by Jack
    It's possible via C# code get an list of methods/delegates that was set to Control? let me explain better.. For example. Assuming some definitions like this: foo.Click += (a, b) => { ... } //.. foo.Click += (A,B) => { ... } And a megic method: var baa = foo.GetEvents("Click"); Returns baa[0] points to (a, b) => { ... } baa[1] points to (A,B) => { ... } My scenery: I make and add dynamically event to some controls inside a loop. I want depending to a boolean value a event of control of index one,will removed by using control.Click -= baa[1] or something like this. I hope this is clear for your. Thanks in advance.

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  • Is there a limitation to the length of the query in mysql?

    - by Bakhtiyor
    I am asking this question because I need to know this limitation as I am generating SELECT query in my PHP script and the part of WHERE in this query is generated inside the loop. Precisely it looks like this $query="SELECT field_names FROM table_name WHERE "; $condition="metadata like \"%$uol_metadata_arr[0]%\" "; for($i=1; $i<count($uol_metadata_arr); $i++){ $condition.=" OR metadata like \"%$uol_metadata_arr[$i]%\" "; } $query.=$condition; $result=mysql_query($query); So, that's why I need to know how long my $query string can be, because the array *$uol_metadata_arr* could contain many items.

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  • Visual Basic 2013 String Replacement

    - by user3707612
    I found this code that replaces a string in a text file. But, I am trying to make it so that it replaces several strings in a text file. My.Computer.FileSystem.WriteAllText("C:\windows\PrinterList2.txt", My.Computer.FileSystem.ReadAllText("C:\windows\PrinterList.txt").Replace("IT", "ADM-IT"), False) For example, I need it to replace "IT" with "ADM-IT" and "AR" with "ADM-AR" and possibly a hundred or so more. How can I get it to loop to do them all? Running this line of code over and over just overwrites the file with the last item for replacement. Thanks in advance.

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  • Help needed in pivoting (SQL Server 2005)

    - by Newbie
    I have a table like ID Grps Vals --- ---- ----- 1 1 1 1 1 3 1 1 45 1 2 23 1 2 34 1 2 66 1 3 10 1 3 17 1 3 77 2 1 144 2 1 344 2 1 555 2 2 11 2 2 22 2 2 33 2 3 55 2 3 67 2 3 77 The desired output being ID Record1 Record2 Record3 --- ------- ------- ------- 1 1 23 10 1 3 34 17 1 45 66 77 2 144 11 55 2 344 22 67 2 555 33 77 I have tried(using while loop) but the program is running slow. I have been asked to do so by using SET based approach. My approach so far is SELECT ID,[1] AS [Record1], [2] AS [Record2], [3] as [Record3] FROM ( Select Row_Number() Over(Partition By ID Order By Vals) records ,* From myTable)x PIVOT (MAX(vals) FOR Grps IN ([1],[2],[3])) p But it is not working. Can any one please help to solve this.(SQL SERVER 2005)

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  • for (Object object : list) [java] construction

    - by EugeneP
    My question, is, whether the sequence of elements picked from a list will always be the same, is this construction behaviour is deterministic for java "List"s - descendants of java.util.List 2) question, if I use for(Object o: list) construction and inside the loop's body increment a variable, will it be the index of list's elements? So, how it goes through list's elements, from 0 to size()-1 or chaotically? List.get(i) will always return this element? 3) question ( I suppose for the 2-nd question the answer will be negative, so:) for (int i=0; i < list.size(); i++) { } is the best way if I need to save the index of an element and later get it back from a list by its id?

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  • how divide herader from binary data

    - by fixo2020
    Hi, I have this code: ofstream dest("test.txt",ios::binary); while (true){ size_t retval = recv (sd, buffer, sizeof(buffer), 0); dest.write(buffer,retval); if(retval <= 0) { delete[] buffer; break;} } Now, the recv() function return 4 bytes each loop right? and buffer contain it, this return all data so, pseudo-header and binary data (image), but I want know how capture only binary data, I know that the end of header are "\n\r" right? but what's are the solution better for make this? I make a function that detect when are "\n\r"? and after how capture binary data? Or, I put all data in memory, and after parse it? but how? I'm desperate :(

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  • Label field problem in the treenode Tag. (Struts2/Ajax)

    - by ryan
    I'm using struts as a framework for a web-app. The following code runs inside a loop where I access the database to retrieve values to be used as nodes for a tree. <s:set name="categoryValue" value= "%{'<%=rs.getString("category")%>'}"> </s:set> <sx:treenode id="child1" label ="%{#categoryValue}"/> The error I get is "/jsp/tree.jsp(249,65) equal symbol expected" However if i give <s:set name="categoryValue" value= "%{'Test'}"> the value Test is obtained. Can anyone tell me how to set the value of the 'label' with strings?

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  • Can someone please clarify the Birthday Effect for me?

    - by Mark
    Please help interpret the Birthday effect as described in Wikipedia: A birthday attack works as follows: Pick any message m and compute h(m). Update list L. Check if h(m) is in the list L. if (h(m),m) is already in L, a colliding message pair has been found. else save the pair (h(m),m) in the list L and go back to step 1. From the birthday paradox we know that we can expect to find a matching entry, after performing about 2^(n/2) hash evaluations. Does the above mean 2^(n/2) iterations through the above entire loop (i.e. 2^(n/2) returns to step 1), OR does it mean 2^(n/2) comparisons to individual items already in L.

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  • Search box inside a div. Django

    - by Juliette Dupuis
    In my django app I display a list of elements (friends name) thanks to a loop: <div> {% for friend in group %} <p>{{ friend.name }} <p> {% endfor %} </div> I would like to create a search box on the top of my list in order to be able to find only the friends the user wants. I would like the search bar does not need to click to send the request (an example is the Airtime searchbox on top of the facebook friends list). I have absolutely no idea on how to do that, and I'm looking for hints or tips to start. Thank you very much for your help.

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  • Reading from CSVs in Python repeatedly?

    - by matt
    I'm trying to check the value of extracted data against a csv I already have. It will only loop through the rows of the CSV once, I can only check one value of feed.items(). Is there a value I need to reset somewhere? Is there a better/more efficient way to do this? Thanks. orig = csv.reader(open("googlel.csv", "rb"), delimiter = ';') goodrows = [] for feed in gotfeeds: for link,comments in feed.items(): for row in orig: print link if link in row[1]: row.append(comments) goodrows.append(row)

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  • Putting a variable inside a string (python)

    - by Gish
    Hi I am quite new to python and this is probably quite a basic question but the help would be much appreciated. I would like to put an int within a string. This is what I am doing at the moment.. end = smooth(data,window_len=40) plot.plot(time[0:len(end)],end) plot.savefig('hanning(40).pdf') #problem line I have to run the program for several different numbers instead of the two 40's. So I'd like to do a loop but inserting the variable like this doesn't work: plot.savefig('hanning',num,'.pdf') Thanks!

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  • UITableViewCell get nil

    - by MTA
    I create a UITableView with custom UITableViewCell,this is how i create the cell in cellForRowAtIndexPath: static NSString *CellIdentifier = @"SongsCell"; SongsCell *cell = (SongsCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil){ UIViewController *vc = [[[UIViewController alloc] initWithNibName:@"SongsCell" bundle:nil] autorelease]; cell = (SongsCell *) vc.view; } now i want to get all cells in the table info (parameter from cell) when a button pressed: for (int i = 0; i < [songTable numberOfRowsInSection:0]; i++) { NSIndexPath *indexPath = [NSIndexPath indexPathForRow:i inSection:0]; UITableViewCell *cell = [songTable cellForRowAtIndexPath:indexPath]; } Now i have a problem that this loop give me for cell a nil for all the cell that currently not seen in the table.

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  • Can i query a List? Java

    - by Nitesh Panchal
    Hello, Say i have List<SomeObject> objList = new ArrayList<SomeObject>(); If someObject contains a field named id. Can we find it through some query like objList.filter('id=2'); wihout looping through the list? If not, then why? This can be so useful method and used as an alternative to write tedious for loop? Just a question that came to my mind so i thought i must clear it here :) Thanks in advance :)

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  • List in C# - passing multiple entries as a single object

    - by Karthick
    Hi, I have a method (C#) public void MethodName(List<Order> Order, int ID) I need to pass this to a main page, in which i know to pass integer value to ID, am not able to pass multiple items in a single list. The List order should have two number entries, (ie. Order.number1 and Order.number2) How should i pass a single list as a parameter to this method containing multiple entries of number1 and 2, so that i can loop thro' and find it. Thanks.

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  • Select_related() backwards relation - auto model population

    - by Nick
    Hi. If I have the following model: class Contact(models.Model) name = models.CharField(max_length=100) ... class ContactAddress(models.Model) line1 = models.CharField(max_length=100) line2 = models.CharField(max_length=100) ... contact = models.ForeignKey(Contact) I now want to grab all Contacts and for the address to be auto populated. What would be the best way to do this? The only way I have found so far is to filter out the Contacts I want and loop around each contact and assign this to Contact.addresses. I then use this for outputting each Contacts address within a template. Is there a better way of doing this? Select_related() almost does what I want, but doesn't seem to be able to work in the opposite direction. Thanks in advance for your help on this one!

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  • can this code be shortened or improved?

    - by user2816683
    Can this be shortened/improved? I'm trying to make a password checker in python. Could the if's be put into a for loop? And if so, how? pw = input("Enter password to test: ") caps = sum(1 for c in pw if c.isupper()) lower = sum(1 for c in pw if c.islower()) nums = sum(1 for c in pw if c.isnumeric()) scr = ['weak', 'medium', 'strong'] r = [caps, lower, nums] if len(pw) < 6: print("too short") elif len(pw) > 12: print("too long") if caps >= 1: if lower >= 1: if nums >= 1: print(scr[2]) elif nums < 1: print("your password is " + scr[1]) elif lower < 1: print("your password strength is " + scr[0]) elif caps < 1: print("your password strength is " + scr[1]) Thanks for any suggestions :D

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