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• Which are your favorite programming language gadgets?

  - by FerranB

  There are some gadgets/features for programming languages that I like a lot because they save a lot of coding or simply because they are magical or nice. Some of my favorites are: C++ increment/decrement operator: my_array[++c]; C++ assign and sum or substract (...): a += b C# yield return: yield return 1; C# foreach: foreach (MyClass x in MyCollection) PLSQL for loop: for c in (select col1, col2 from mytable) PLSQL pipe row: for i in 1..x loop pipe row(i); end loop; Python Array access operator: a[:1] PLSQL ref cursors. Which are yours?

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• Windbg + IDA: calculate an address in a module

  - by Benjamin

  Hi all, I'm debugging remotely a windows XP machine. One of my drivers is loaded at address 0xb2c4c000 up to 0xb2cb9680. Now when I open my driver in IDA, the offset I want to set a breakpoint on is at 00017619. How can I effectively match my IDA address into windbg? I've tried the obvious which is to sum 0xb2c4c000 + 00017619 = 0xB2C635F7 and disassemble that address using the 'u' command in windbg. But the results did not match the assembly in IDA. On the side question: is there a way to cancel a command that is running in windbg? Several times I've ran commands that took ages to process, I would like to be able to cancel them if needed. So I can keep working. Thanks for your time.

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• How can I call model methods or properties from Django Admin?

  - by kg

  Is there a natural way to display model methods or properties in the Django admin site? In my case I have base statistics for a character that are part of the model, but other things such as status effects which affect the total calculation for that statistic: class Character(models.Model): base_dexterity = models.IntegerField(default=0) @property def dexterity(stat_name): total = self.base_dexterity total += sum(s.dexterity for s in self.status.all()]) return total It would be nice if I could display the total calculated statistic alongside the field to change the base statistic in the Change Character admin page, but it is not clear to me how to incorporate that information into the page.

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• Converting IPv4 or IPv6 address to a long for comparisons

  - by Justin Akehurst

  In order to check if an IPv4 or IPv6 address is within a certain range, I've got code that takes an IPv4 address, turns that into a long, then does that same conversion on the upper/lower bound of the subnet, then checks to see if the long is between those values. I'd like to be able to do the same thing for IPv6, but saw nothing in the Python 2.6 standard libraries to allow me to do this, so I wrote this up: import socket, struct from array import array def ip_address_to_long(address): ip_as_long = None try: ip_as_long = socket.ntohl(struct.unpack('L', socket.inet_pton(socket.AF_INET, address))[0]) except socket.error: # try IPv6 try: addr = array('L', struct.unpack('!4L', socket.inet_pton(socket.AF_INET6, address))) addr.reverse() ip_as_long = sum(addr[i] << (i * 32) for i in range(len(addr))) except socket.error as se: raise ValueError('Invalid address') except Exception as e: print str(e) return ip_as_long My question is: Is there a simpler way to do this that I am missing? Is there a standard library call that can do this for me?

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• Where to execute extra logic for linq to entities query?

  - by Inez

  Let say that I want to populate a list of CustomerViewModel which are built based on Customer Entity Framework model with some fields (like Balance) calculated separately. Below I have code which works for lists - it is implemented in my service layer, but also I want to execute this code when I just get one item from the database and execute is as well in different services where I'm accessing Customers data as well. How should I do this to ensure performance but to to not duplicate code - the one for calculating Balance? public List<CustomerViewModel> GetCustomerViewModelList() { IQueryable<CustomerViewModel> list = from k in _customerRepository.List() select new CustomerViewModel { Id = k.Id, Name = k.Name, Balance = k.Event.Where(z => z.EventType == (int) EventTypes.Income).Sum(z => z.Amount) }; return list.ToList(); }

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• total number of magic square from 9 numbers

  - by Peeyush

  9 numbers need to be arranged in a magic number square. A magic number square is a square of numbers that is arranged such that every row and column has the same sum.(condition for diagonal has been relaxed) For example: 1 2 3 3 2 1 2 2 2 How do we calculate total number of distinct magic square from 9 numbers. Two magic number squares are distinct if they differ in value at one or more positions. For example, there is only one magic number square that can be made of 9 instances of the same number. e.g. for these 9 numbers { 4, 4, 4, 4, 4, 4, 4, 4, 4 }, answer should be 1. Also the complexity should be optimal. Do we need to iterate through all the permutations , discarding if a[0]+a[1]+a[2] %3!=0 such combinations ? moreover how do we remove duplicate magic square?

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• Fibonacci sequence subroutine returning one digit too high...PERL

  - by beProactive

  #!/usr/bin/perl -w use strict; sub fib { my($num) = @_; #give $num to input array return(1) if ($num<=1); #termination condition return($num = &fib($num-1) + &fib($num-2)); #should return sum of first "n" terms in the fibonacci sequence } print &fib(7)."\n"; #should output 20 This subroutine should be outputting a summation of the first "x" amount of terms, as specified by the argument to the sub. However, it's one too high. Does this have something to do with the recursion? Thanks.

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• Batch update records in Grails

  - by UltraVi01

  I have to calculate a "total" for each user based on individual actions -- that is, a User hasMany Actions and each Action has a point. So I need to basically get a sum of all the points on all the actions. Actions are added and subtracted regularly. Since this can be a rather heavy operation, it's not feasible that I execute the "total" each time I need it. Therefore, I am thinking of running the operation once a day for each user and storing the total points on the User as an int. Because I have thousands of users, I am trying to figure out the best way to do this. Should I basically iterate through all the users and call User.save() each time, or is there some kind of batch update mechanism I can use in Grails / GORM?

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• How can I build my SQL query from these tables?

  - by vee

  Hi All, I'm thinking of building query from these 2 tables (on SQL Server 2008). I have 2 tables as shown below: Table 1 MemberId . MemberName . Percentage . Amount1 00000001 AAA 1.0 100 00000002 BBB 1.2 800 00000003 ZZZ 1.0 700 Table 2 MemberId . MemberName . Percentage . Amount2 00000002 BBB 1.5 500 00000002 BBB 1.6 100 00000002 BBB 1.6 150 The result I want is MemberId . MemberName . Percentage . Amount . NettAmount 00000001 AAA 1.0 100 100 00000002 BBB 1.2 800 50 <-- 800-(500+100+150) 00000002 BBB 1.5 500 500 00000002 BBB 1.6 650 650 00000003 ZZZ 1.0 700 700 50 comes from 800 in Table1 minus sum of Amount2 in table2 for MemberID=00000002 Plz someone help me to build the query to reach this result. Thank you in advance.

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• div width problem...problem is cross browser

  - by Aakash Sahai

  hello ol. I have a div having two buttons inside it as |Add| and |Cancel|. I didnt set any width to that div intially and as a result they were displayed vertically not in horizontal.then i add width in % to 11.5%.now the display is ok in moz but not in chrome and ie.i cant use pixels neither in height nor width.problem explanied by example |_______| // a textbox |Add| //initially with no width |Cancel| //after width to 11.5% in moz |_______| |Add| |Cancel| //after width to 11.5% in chrome and ie |_______| |Add| |Cancel| so u can see that in moz it is aligned to the above textbox but not in ie and chrome.hope sum ie hack or chrome hack may lead to correct result..or ONLY a MOZ hack..

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• Pure Java open-source libraries for portfolio selection (= constrained, non-linear optimization)?

  - by __roland__

  Does anyone know or has experience with a pure Java library to select portfolios or do some similar kinds of quadratic programming with constraints? There seems to be a lot of tools, as already discussed elsewhere - but what I would like to use is a pure Java implementation. Since I want to call the library from within another open-source software with a BSD-ish license I would prefer LGPL over GPL. Any help is appreciated. If you don't know such libraries, which is the most simple algorithm you would suggest to implement? It has to cope with an inequality constraint (all x_i = 0) and an equality constraint (sum of all x_i = 1).

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• mySQL Left Join on multiple tables

  - by Jarrod

  Hi I'm really struggling with this query. I have 4 tables (http://oberto.co.nz/db-sql.png): Invoice_Payement, Invoice, Client and Calendar. I'm trying to create a report by summing up the 'paid_amount' col, in Invoice_Payment, by month/year. The query needs to include all months, even those with no data There query needs the condition (Invoice table): registered_id = [id] I have tried with the below query, which works, but falls short when 'paid_date' does not have any records for a month. The outcome is that month does not show in the results I added a Calendar table to resolved this but not sure how to left join to it. SELECT MONTHNAME(Invoice_Payments.date_paid) as month, SUM(Invoice_Payments.paid_amount) AS total FROM Invoice, Client, Invoice_Payments WHERE Client.registered_id = 1 AND Client.id = Invoice.client_id And Invoice.id = Invoice_Payments.invoice_id AND date_paid IS NOT NULL GROUP BY YEAR(Invoice_Payments.date_paid), MONTH(Invoice_Payments.date_paid) Please see the above link for a basic ERD diagram of my scenario. Thanks for reading. I've posted this Q before but I think I worded it badly.

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• MySQL indexes: how do they work?

  - by bob-the-destroyer

  I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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• How to apply coding methodologies and practices to non-coding work?

  - by Dan

  I can talk for hours about best-practice, source control, change management, feature tracking, development cycles and the lot, but most of what I've learnt or read seems to apply to nuts-and-bolts programming of compiled applications. You know, ASCII files that gets turned into 1s and 0s. How does one apply the same discipline and wisdom to working in environments that are point-and-click, config-centric. I'm thinking of CMSs and specifically, my current 9 to 5, SharePoint. Traditional practices of source control, dev-staging-production seem to break down since we're not working with code, and the live environment changes with user input. So to sum up a rather lengthy question, what works in a no-code environment?

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• Vectorizing sums of different diagonals in a matrix

  - by reve_etrange

  I want to vectorize the following MATLAB code. I think it must be simple but I'm finding it confusing nevertheless. r = some constant less than m or n [m,n] = size(C); S = zeros(m-r,n-r); for i=1:m-r for j=1:n-r S(i,j) = sum(diag(C(i:i+r-1,j:j+r-1))); end end The code calculates a table of scores, S, for a dynamic programming algorithm, from another score table, C. The diagonal summing is to generate scores for individual pieces of the data used to generate C, for all possible pieces (of size r). Thanks in advance for any answers! Sorry if this one should be obvious...

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• How do we know if a query is cache or retrieved from database?

  - by Hadi

  For example: class Product has_many :sales_orders def total_items_deliverable self.sales_orders.each { |so| #sum the total } #give back the value end end class SalesOrder def self.deliverable # return array of sales_orders that are deliverable to customer end end SalesOrder.deliverable #give all sales_orders that are deliverable to customer pa = Product.find(1) pa.sales_orders.deliverable #give all sales_orders whose product_id is 1 and deliverable to customer pa.total_so_deliverable The very point that i'm going to ask is: how many times SalesOrder.deliverable is actually computed, from point 1, 3, and 4, They are computed 3 times that means 3 times access to database so having total_so_deliverable is promoting a fat model, but more database access. Alternatively (in view) i could iterate while displaying the content, so i ends up only accessing the database 2 times instead of 3 times. Any win win solution / best practice to this kind of problem ?

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• Windows Azure Table Storage LINQ Operators

  - by Ryan Elkins

  Currently Table Storage supports From, Where, Take, and First. Are there plans to support any of the other 29 operators? If we have to code for these ourselves, how much of a performance difference are we looking at to something similar via SQL and SQL Server? Do you see it being somewhat comparable or will it be far far slower if I need to do a Count or Sum or Group By over a gigantic dataset? I like the Azure platform and the idea of cloud based storage. I like Windows Azure for the amount of data it can store and the schema-less nature of table storage. SQL Azure just won't work due to the high cost to storage space.

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• What would make offsetParent null?

  - by Brian Ramsay

  I am trying to do positioning in JavaScript. I am using a cumulative position function based on the classic quirksmode function that sums offsetTop and offsetLeft for each offsetParent until the top node. However, I am running into an issue where the element I'm interested in has no offsetParent in Firefox. In IE offsetParent exists, but offsetTop and offsetLeft all sum up to 0, so it has the same problem in effect as in Firefox. What would cause an element that is clearly visible and usable on the screen to not have an offsetParent? Or, more practically, how can I find the position of this element in order to place a drop-down beneath it?

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• Use LINQ and C# to make a new List from an old List

  - by Addie

  This should be pretty simple, but I am new at LINQ. I have a List of FillList structs. I'd like to use LINQ to create a new List where instead of having the number of buys and sells, I would have one variable containing the sum. For example, if the FillStruct structure has buy = 4 and sell = 2 then the NewFillStruct structure will have numlong = 2. If the FillStruct structure has buy = 2 and sell = 4 then the NewFillStruct structure will have numlong = -2. Here are the structures. struct FillStruct { int buy; int sell; string date; } struct NewFillStruct { int numlong; string date; }

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• Python beginner, strange output problem

  - by Protean

  I'm having a weird problem with the following piece of code. from math import sqrt def Permute(array): result1 = [] result2 = [] if len(array) <= 1: return array for subarray in Permute(array[1:]): for i in range(len(array)): temp1 = subarray[:i]+array[0]+subarray[i:] temp2 = [0] for num in range(len(array)-1): temp2[0] += (sqrt(pow((temp1[num+1][1][0]-temp1[num][1][0]),2) + pow((temp1[num+1][1][1]-temp1[num][1][1]),2))) result1.append(temp1+temp2) return result1 a = [['A',[50,1]]] b = [['B',[1,1]]] c = [['C',[100,1]]] array = [a,b,c] result1 = Permute(array) for i in range(len(result1)): print (result1[i]) print (len(result1)) What it does is find all the permutations of the points abc and then returns them along with the sum of the distances between each ordered point. It does this; however, it also seems to report a strange additional value, 99. I figure that the 99 is coming from the computation of the distance between point a and c but I don't understand why it is appearing in the final output as it does.

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• add method to reflection-object and named-scopes

  - by toy

  I Like to add a method to my has_many relation in the way that it is applyed on the relation object. I got an Order wich :has_many line_items I like to write things like order.line_items.calculate_total # returns the sum of line_items this I could do with: :has_many line_items do def calculate_total ... end end but this would not be applyed to named_scopes like payalbes_only: order.line_items.payables_only.calculate_total here calculate total would receive all line_items of order and not the scoped ones from payables_only-scope. My log tells me that the paybles_only scope is even not applied to the sql.

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• Perform Grouping of Resultset in Code

  - by NinjaBomb

  Stackoverflowers, I have a resultset from a SQL query in the form of: Category Column2 Column3 A 2 3.50 A 3 2 B 3 2 B 1 5 ... I need to group the resultset based on the Category column and sum the values for Column2 and Column3. I have to do it in code because I cannot perform the grouping in the SQL query that gets the data due to the complexity of the query (long story). This grouped data will then be displayed in a table. I have it working for specific set of values in the Category column, but I would like a solution that would handle any possible values that appear in the Category column. I know there has to be a straightforward, efficient way to do it but I cannot wrap my head around it right now. How would you accomplish it?

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• filter that uses elements from two arrays at the same time

  - by Gacek

  Let's assume we have two arrays of the same size - A and B. Now, we need a filter that, for a given mask size, selects elements from A, but removes the central element of the mask, and inserts there corresponding element from B. So the 3x3 "pseudo mask" will look similar to this: A A A A B A A A A Doing something like this for averaging filter is quite simple. We can compute the mean value for elements from A without the central element, and then combine it with a proper proportion with elements from B: h = ones(3,3); h(2,2) =0; h = h/sum(h(:)); A_ave = filter2(h, A); C = (8/9) * A_ave + (1/9) * B; But how to do something similar for median filter (medfilt2 or even better for ordfilt2)

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• Does the JPQL avg aggregate function work with Integers?

  - by Kyle Renfro

  I have a JPA 2 Entity named Surgery. It has a member named transfusionUnits that is an Integer. There are two entries in the database. Executing this JPQL statement: Select s.transfusionUnits from Surgery s produces the expected result: 2 3 The following statement produces the expected answer of 5: Select sum(s.transfusionUnits) from Surgery s I expect the answer of the following statement to be 2.5, but it returns 2.0 instead. Select avg(s.transfusionUnits) from Surgery s If I execute the statement on a different (Float) member, the result is correct. Any ideas on why this is happening? Do I need to do some sort of cast in JPQL? Is this even possible? Surely I am missing something trivial here.

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• Count the number of rows of a CSV file, with d3.js

  - by user2934073

  Suppose I have this CSV file Day,What 2013-10-27,Apple 2013-10-27,Cake 2013-10-27,Apple 2013-10-28,Apple 2013-10-28,Apple 2013-10-28,Blueberry 2013-10-28,Orange I would like to drawn with D3.js a time-series graph. All I need to do is to display the sum of the number of rows for each day. As an example, the 27 of November should have 3 as value, the 28th should have 4. Is there a way I can archive it? I've been trying to create a new dataset out of the CSV one with no positive results. var dataset; d3.csv("data.csv", function(d) { return { Day: new Date(d.Day), What: d.What }; }, function(error, rows) { dataset = rows; // I SUPPOSE THE FUNCTION THAT GENERATE THE NEW DATASET SHOULD GO THERE });

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