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  • Should try...catch go inside or outside a loop?

    - by mmyers
    I have a loop that looks something like this: for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } This is the main content of a method whose sole purpose is to return the array of floats. I want this method to return null if there is an error, so I put the loop inside a try...catch block, like this: try { for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } } catch (NumberFormatException ex) { return null; } But then I also thought of putting the try...catch block inside the loop, like this: for(int i = 0; i < max; i++) { String myString = ...; try { float myNum = Float.parseFloat(myString); } catch (NumberFormatException ex) { return null; } myFloats[i] = myNum; } So my question is: is there any reason, performance or otherwise, to prefer one over the other? EDIT: The consensus seems to be that it is cleaner to put the loop inside the try/catch, possibly inside its own method. However, there is still debate on which is faster. Can someone test this and come back with a unified answer? (EDIT: did it myself, but voted up Jeffrey and Ray's answers)

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  • Fatal error: Cannot use string offset as an array

    - by learner
    Array ( [0] = Array ( [auth_id] = 1 [auth_section] = Client Data Base [auth_parent_id] = 0 [auth_admin] = 1 [sub] = Array ( [0] = Array ( [auth_id] = 2 [auth_section] = Client Contact [auth_parent_id] = 1 [auth_admin] = 1 ) ) ) [1] => Array ( [auth_id] => 6 [auth_section] => All Back Grounds [auth_parent_id] => 0 [auth_admin] => ,4 [sub] => Array ( [0] => Array ( [auth_id] => 7 [auth_section] => Edit Custom [auth_parent_id] => 6 [auth_admin] => 1 ) ) ) [2] => Array ( [auth_id] => 20 [auth_section] => Order Mail [auth_parent_id] => 0 [auth_admin] => 1 [sub] => ) } When I process the sub inner array it shows this error how can I avoid that :)

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  • C++ Loop - Need variable to accumulate sum

    - by user1780064
    I'm writing a program to ask the user to enter a value between 5 and 21 (inclusive). If the number entered is not in this range, it prints, "Please try again". If the number is within the range, I need to take that number, and print the sum of all the numbers from 1 to the value entered. So if the user entered "7", the sum would be "28". I successfully wrote the first loop, in the case of the number not being within the range, but cannot figure out how to run the second loop- whether to use a while, do-while, or for loop. Please advise. #include <iostream> int main () { int uservalue; int count; int sum; //Prompt user for input do { cout << "Enter a value from 5 to 21: "; cin >> uservalue; if (uservalue < 5 || uservalue > 21) cout << "Value out of range. Try again..." << endl; } while (uservalue < 5 || uservalue > 21); cout << endl; //Loop to accumulate sum for (count = 1, count < uservalue, count++;) { sum = uservalue + count; if (uservalue <= 5 || uservalue <= 21) cout << the sum is " << sum << endl; } return 0; }

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  • Pulling $_GET data and creating multidimensional array using loop

    - by Chris J
    I'm creating a checkout for customers and the data about what's in their cart is being sent to a page (for just now) via $_GET. I want to extract that data and then populate a multidimensional array with it using a loop. Here's how I'm naming the data: $itemCount = $_GET['itemCount']; $i = 1; while ($i <= $itemCount) { ${'item_name_'.$i} = $_GET["item_name_{$i}"]; ${'item_quantity_'.$i} = $_GET["item_quantity_{$i}"]; ${'item_price_'.$i} = $_GET["item_price_{$i}"]; //echo "<br />Name: " .${'item_name_'.$i}. " - Quantity: " .${'item_quantity_'.$i}. " - Price: ".${'item_price_'.$i}; $i++; } From here I'd like to create a multidimensional array like such: Array ( [Item_1] => Array ( [item_name] => Shoe [item_quantity] => 2 [item_price] => 40.00 ) [Item_2] => Array ( [item_name] => Bag [item_quantity] => 1 [item_price] => 60.00 ) [Item_3] => Array ( [item_name] => Parrot [item_quantity] => 4 [item_price] => 90.00 ) . . . ) What I'd like to know is if there is a way I can create this array in the existing while loop? I'm aware of being able to add data to an array like $data = [] after delacring an empty array but the actual syntax eludes me. Maybe I'm completely off the right track and there is a better way of doing it? Thanks

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

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

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  • Substituting variables in a loop?

    - by jksl
    I am trying to write a loop in R but I think the nomenclature is not correct as it does not create the new objects, here is a simplified example of what I am trying to do: for i in (1:8) { List_i <-List colsToGrab_i <-grep(predefinedRegex_i, colnames(List_i$table)) List_i$table <- List_i$table[,predefinedRegex_i] } I have created 'predefinedRegex'es 1:8 which the grep should use to search The loop creates an object called "List_i" and then fails to find "predefinedRegex_i". I have tried putting quotes around the "i" and $ in front of the i but these do not work. Any help much appreciated. Thank you.

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  • Another php array looping question

    - by Dan
    Been battling with this one for what seems, like forever. I have an array: $url_array It contains this info: Array ( [ppp] => Array ( [0] => stdClass Object ( [id] => 46660 [entity_id] => 0 [redirect_url] => http://www.google.com [type] => Image ) [1] => stdClass Object ( [id] => 52662 [entity_id] => 0 [pixel_redirect_url] => http://www.yahoo.com [type] => Image ) [2] => stdClass Object ( [id] => 53877 [entity_id] => 0 [redirect_url] => http://www.msn.com [pixel_type] => Image ) ) [total_count] => 3 ) I need to loop through it, and do things to each variable. I can get this to work: foreach ($piggies_array as $key => $value) { $id = $value[0]->id; $redirect_url = $value[0]->redirect_url; } Not unsurprisingly, it's only echoing the first value of those variables, but no matter what I try I cannot get it to loop through: $value->redirect_url; $value=>redirect_url; I would appreciate any help.

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  • Is "}while(0);" always equal to "break;}while(1);" ?

    - by Hernán Eche
    I have compared gcc assembler output of do{ //some code }while(0); with do{ //some code break; }while(1); The output is equal, with or without optimization but.. It's always that way? No experiment can prove theories, they can only show they are wrong And because (I hope) programming is not an experimental science, and results can be predicted (at least simple things) I want to be sure next time I reeplace a break;}while(1); for the clearer (and less risky) while(0); Thank you for reading

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  • Retrieve array key passed on value PHP

    - by Doodle
    I have the following array $group= array( [0] => 'apple', [1] => 'orange', [2] => 'gorilla' ); I run the array group through an for each function and when the loop hits values of gorilla I want it to spit out the index of gorilla foreach( $group as $key){ if ($key==gorilla){ echo //<------ the index of gorilla } }

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  • How to parse a string (by a "new" markup) with R ?

    - by Tal Galili
    Hi all, I want to use R to do string parsing that (I think) is like a simplistic HTML parsing. For example, let's say we have the following two variables: Seq <- "GCCTCGATAGCTCAGTTGGGAGAGCGTACGACTGAAGATCGTAAGGtCACCAGTTCGATCCTGGTTCGGGGCA" Str <- ">>>>>>>..>>>>........<<<<.>>>>>.......<<<<<.....>>>>>.......<<<<<<<<<<<<." Say that I want to parse "Seq" According to "Str", by using the legend here Seq: GCCTCGATAGCTCAGTTGGGAGAGCGTACGACTGAAGATCGTAAGGtCACCAGTTCGATCCTGGTTCGGGGCA Str: >>>>>>>..>>>>........<<<<.>>>>>.......<<<<<.....>>>>>.......<<<<<<<<<<<<. | | | | | | | || | +-----+ +--------------+ +---------------+ +---------------++-----+ | Stem 1 Stem 2 Stem 3 | | | +----------------------------------------------------------------+ Stem 0 Assume that we always have 4 stems (0 to 3), but that the length of letters before and after each of them can very. The output should be something like the following list structure: list( "Stem 0 opening" = "GCCTCGA", "before Stem 1" = "TA", "Stem 1" = list(opening = "GCTC", inside = "AGTTGGGA", closing = "GAGC" ), "between Stem 1 and 2" = "G", "Stem 2" = list(opening = "TACGA", inside = "CTGAAGA", closing = "TCGTA" ), "between Stem 2 and 3" = "AGGtC", "Stem 3" = list(opening = "ACCAG", inside = "TTCGATC", closing = "CTGGT" ), "After Stem 3" = "", "Stem 0 closing" = "TCGGGGC" ) I don't have any experience with programming a parser, and would like advices as to what strategy to use when programming something like this (and any recommended R commands to use). What I was thinking of is to first get rid of the "Stem 0", then go through the inner string with a recursive function (let's call it "seperate.stem") that each time will split the string into: 1. before stem 2. opening stem 3. inside stem 4. closing stem 5. after stem Where the "after stem" will then be recursively entered into the same function ("seperate.stem") The thing is that I am not sure how to try and do this coding without using a loop. Any advices will be most welcomed.

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  • JQuery going through a set of UL and dynamically set ids incremently on each one

    - by Calibre2010
    I have an unordered list which contains serveral items called 'oListItems' the UL has a class but no id. The class OuteroListItems contains many of oListitems oList.AppendFormat("<ul class='OuteroListItems'>"); oList.AppendFormat("<li>"); oList.AppendFormat("<ul class='oListItems'>"); oList.AppendFormat("<li>" + s.sName + "</li>"); oList.AppendFormat("<li>" + s.eName + "</li>"); oList.AppendFormat("<li>" + s.SDate + "</li>"); oList.AppendFormat("<li>" + s.EDate + "</li>"); oList.AppendFormat("</ul>"); oList.AppendFormat("</li>"); oList.AppendFormat("</ul>"); I want for each .oListItem class that gets retrieved, add dynamically an id to it. var o = $(".oListItem"); $.each(o, function (){ var f = $(this).attr("id", 'listItem' + i); i++; }); wasent sure on the approach, this is what I have so far?

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  • If Key Value pair exists in multidimensional array.. How to?

    - by Daniel White
    I have a codeigniter shopping cart going and its "cart" array is the following: Array ( [a87ff679a2f3e71d9181a67b7542122c] => Array ( [rowid] => a87ff679a2f3e71d9181a67b7542122c [id] => 4 [qty] => 1 [price] => 12.95 [name] => Maroon Choir Stole [image] => 2353463627maroon_3.jpg [custprod] => 0 [subtotal] => 12.95 ) [8f14e45fceea167a5a36dedd4bea2543] => Array ( [rowid] => 8f14e45fceea167a5a36dedd4bea2543 [id] => 7 [qty] => 1 [price] => 12.95 [name] => Shiny Red Choir Stole [image] => 2899638984red_vstole_1.jpg [custprod] => 0 [subtotal] => 12.95 ) [eccbc87e4b5ce2fe28308fd9f2a7baf3] => Array ( [rowid] => eccbc87e4b5ce2fe28308fd9f2a7baf3 [id] => 3 [qty] => 1 [price] => 14.95 [name] => Royal Blue Choir Stole [image] => 1270984005royal_vstole.jpg [custprod] => 1 [subtotal] => 14.95 ) ) My goal is to loop through this multidimensional array some how and if ANY product with the key value pair "custprod == 1" exists, then my checkout page will display one thing, and if no custom products are in the cart it displays another thing. Any help is appreciated. Thanks.

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  • ForEach loop in Mathematica.

    - by dreeves
    I'd like something like this: ForEach[i_, {1,2,3}, Print[i] ] Or, more generally, to destructure arbitrary stuff in the list you're looping over, like: ForEach[{i_, j_}, {{1,10}, {2,20}, {3,30}}, Print[i*j] ] (Meta-question: is that a good way to call a ForEach loop, with the first argument a pattern like that?) ADDED: Some answerers have rightly pointed out that usually you want to use Map or other purely functional constructs and eschew a non-functional programming style where you use side effects. I agree! But here's an example where I think this ForEach construct is supremely useful: Say I have a list of options (rules) that pair symbols with expressions, like attrVals = {a -> 7, b -> 8, c -> 9} Now I want to make a hash table where I do the obvious mapping of those symbols to those numbers. I don't think there's a cleaner way to do that than ForEach[a_ -> v_, attrVals, h[a] = v] ADDED: I just realized that to do ForEach properly, it should support Break[] and Continue[]. I'm not sure how to implement that. Perhaps it will need to somehow be implemented in terms of For, While, or Do since those are the only loop constructs that support Break[] and Continue[]. If anyone interested in this wants to ask about that as a separate question, please do!

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  • Rails: How to name and create unique divs within a loop?

    - by sscirrus
    I have a view with a div that is looped many times. Each of the created divs need to have a unique ID so I can access them specifically (at the moment, all my divs have the same ID specified in html so whenever I try to access a specific div it just finds the first one). This is the version that I currently have (multiple 'rowBox'es are not discernible). <% @customers.each do |customer| %> <div id="customer" class="rowBox"> ... </div> <% end %> I would like to be able to do something like: <% @customers.each do |customer| %> <div id="box<%=customer.id%>"> ... </div> <% end %> This doesn't seem to work. Any ideas on how to accomplish this?

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  • How to use an adjacency matrix to determine which rows to 'pass' to a function in r?

    - by dubhousing
    New to R, and I have a long-ish question: I have a shapefile/map, and I'm aiming to calculate a certain index for every polygon in that map, based on attributes of that polygon and each polygon that neighbors it. I have an adjacency matrix -- which I think is the same as a "1st-order queen contiguity weights matrix", although I'm not sure -- that describes which polygons border which other polygons, e.g., POLYID A B C D E A 0 0 1 0 1 B 0 0 1 0 0 C 1 1 0 1 0 D 0 0 1 0 1 E 1 0 0 1 0 The above indicates, for instance, that polygons 'C' and 'E' adjoin polygon 'A'; polygon 'B' adjoins only polygon 'C', etc. The attribute table I have has one polygon per row: POLYID TOT L10K 10_15K 15_20K ... A 500 24 30 77 ... Where TOT, L10K, etc. are the variables I use to calculate an index. There are 525 polygons/rows in my data, so I'd like to use the adjacency matrix to determine which rows' attributes to incorporate into the calculation of the index of interest. For now, I can calculate the index when I subset the rows that correspond to one 'bundle' of neighboring polygons, and then use a loop (if it's of interest, I'm calculating the Centile Gap Index, a measure of local income segregation). E.g., subsetting the 'neighborhood' of the Detroit City Schools: Detroit <- UNSD00[c(142,150,164,221,226,236,295,327,157,177,178,364,233,373,418,424,449,451,487),] Then record the marginal column proportions and a running total: catprops <- vector() for(i in 4:19) { catprops[(i-3)]<-sum(Detroit[,i])/sum(Detroit[,3]) } catprops <- as.data.frame(catprops) catprops[,2]<-cumsum(catprops[,1]) Columns 4:19 are the necessary ones in the attribute table. Then I use the following code to calculate the index -- note that the loop has "i in 1:19" because the Detroit subset has 19 polygons. cgidistsum <- 0 for(i in 1:19) { pranks <- vector() for(j in 4:19) { if (Detroit[i,j]==0) pranks <- append(pranks,0) else if (j == 4) pranks <- append(pranks,seq(0,catprops[1,2],by=catprops[1,2]/Detroit[i,j])) else pranks <- append(pranks,seq(catprops[j-4,2],catprops[j-3,2],by=catprops[j-3,1]/Detroit[i,j])) } distpranks <- vector() distpranks<-abs(pranks-median(pranks)) cgidistsum <- cgidistsum + sum(distpranks) } cgi <- (.25-(cgidistsum/sum(Detroit[,3])))/.25 My apologies if I've provided more information than is necessary. I would really like to exploit the adjacency matrix in order to calculate the CGI for each 'bundle' of these rows. If you happen to know how I could started with this, that would be great. and my apologies for any novice mistakes, I'm new to R!

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  • Change class of parent div if radio input checked

    - by xxstevenxo
    I've been searching and searching google for answers to my question but have been unsuccessful so far. I'm hoping one of you guys could give me some assistance. I have 10 divs with the class name "dividend" holding a table with the classname/id of "container" then two smaller tables inside that. Within the container table at the bottom is a hidden radio button with the name "page1". I wrote an onClcick for the container table so the user can select the whole table instead of the radio button, but not I'm trying to change the style of the selected container so the users know they have selected it. I have tried a few different methods and I'm able to change the style to the new class by just writing document.getElementById('container').className = 'selected'; But because all 10 divs share the same name it will only change the style of the first element it finds. So I tried writing this loop to check if there are any selected radios in the document then to change the else name the style as the default. I'm sure its something stupid but I'm pretty stumped atm.. Any help would be appreciated. Thanks. selected = function () { var divs = document.getElementByTagName('DIV'), div, tbl, rad, stat, i; for (i = 0; i < divs.length; i++) { div = divs.id; if (div == 'dividend') { tbl = div.getElementById('container'); rad = tbl.getElementByTagName('INPUT'); if (rad.checked = true) { tbl.className = 'selected'; } } } };

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  • How can I loop through each of the days of a given week in Ruby?

    - by Angela
    I am defining monday and friday using the following: @monday = Date.today.at_beginning_of_week @friday = 5.days.since(@monday) But I actually need, for any given day, to loop through Monday, Tuesday, Wednesday and take that date and put the output into a column. <th>Monday</th> <th>Tuesday</th> etcetera A given row, for example, would be: <tr><td>value(monday)</td><td>value(tuesday)</td><td>value(wednesday)</td></tr> This is where value is a method that takes args date. What's the cleanest way to do this? Thanks.

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  • while loop / string input not working java

    - by Mikeecb
    I have looked online and all of the tutorials / questions have pointed me to this. I can't see why this isn't working. Any help would be much appreciated. Thanks import java.util.*; public class test { static Scanner userInput = new Scanner(System.in); public static void main(String[] args) { String textEntered = userInput.next(); if (textEntered == "hello") { System.out.println("Hello to you too!"); } } } I enter "hello" but nothing is printed. Also I have tried next() and nextLine();

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