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  • Modify columns in a data frame in R more cleanly - maybe using with() or apply()?

    - by Mittenchops
    I understand the answer in R to repetitive things is usually "apply()" rather than loop. Is there a better R-design pattern for a nasty bit of code I create frequently? So, pulling tabular data from HTML, I usually need to change the data type, and end up running something like this, to convert the first column to date format (from decimal), and columns 2-4 from character strings with comma thousand separators like "2,400,000" to numeric "2400000." X[,1] <- decYY2YY(as.numeric(X[,1])) X[,2] <- as.numeric(gsub(",", "", X[,2])) X[,3] <- as.numeric(gsub(",", "", X[,3])) X[,4] <- as.numeric(gsub(",", "", X[,4])) I don't like that I have X[,number] repeated on both the left and ride sides here, or that I have basically the same statement repeated for 2-4. Is there a very R-style way of making X[,2] less repetitive but still loop-free? Something that sort of says "apply this to columns 2,3,4---a function that reassigns the current column to a modified version in place?" I don't want to create a whole, repeatable cleaning function, really, just a quick anonymous function that does this with less repetition.

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  • What's the best way to avoid try...catch...finally... in my unit tests?

    - by Bruce Li
    I'm writing many unit tests in VS 2010 with Microsoft Test. In each test class I have many test methods similar to below: [TestMethod] public void This_is_a_Test() { try { // do some test here // assert } catch (Exception ex) { // test failed, log error message in my log file and make the test fail } finally { // do some cleanup with different parameters } } When each test method looks like this I fell it's kind of ugly. But so far I haven't found a good solution to make my test code more clean, especially the cleanup code in the finally block. Could someone here give me some advices on this? Thanks in advance.

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  • Is concatenating with an empty string to do a string conversion really that bad?

    - by polygenelubricants
    Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it: char c1, c2; // ... String s = "" + c1 + c2; I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because: I prefer using language feature instead of API call if possible In general, isn't the language usually more stable than the API? If language feature only hides API call, then even stronger reason to prefer it! More abstract! Hiding is good! I like that the c1 and c2 are visually on the same level String.valueOf(c1) + c2 suggests something is special about c1 It's shorter. Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +? Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type: this("" + detailMessage);

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  • typeof === "undefined" vs. != null

    - by Thor Thurn
    I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. It's needed because 'undefined' could be renamed, though. My question is: How is that code any better than this approach: if (input != null) { // do stuff } As far as I know, you can't redefine null, so it's not going to break unexpectedly. And, because of the type-coercion of the != operator, this checks for both undefined and null... which is often exactly what you want (e.g. for optional function parameters). Yet this form does not seem widespread, and it even causes JSLint to yell at you for using the evil != operator. Why is this considered bad style?

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  • Python - what's your conventions to declare your attributes in a class ?

    - by SeyZ
    Hello, In Python, I can declare attributes all over the class. For example : class Foo: def __init__(self): self.a = 0 def foo(self): self.b = 0 It's difficult to retrieve all attributes in my class when I have a big class with a lot of attributes. Is it better to have the following code (a) or the next following code (b) : a) Here, it's difficult to locate all attributes : class Foo: def __init__(self): foo_1() foo_2() def foo_1(self): self.a = 0 self.b = 0 def foo_2(self): self.c = 0 b) Here, it's easy to locate all attributes but is it beautiful ? class Foo: def __init__(self): (self.a, self.b) = foo_1() self.c = foo_2() def foo_1(self): a = 0 b = 0 return (a, b) def foo_2(self): c = 0 return c In a nutshell, what is your conventions to declare your attributes in a class ?

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  • Factory vs instance constructors

    - by Neil N
    I can't think of any reasons why one is better than the other. Compare these two implementations: public class MyClass { public myClass(string fileName) { // some code... } } as opposed to: public class MyClass { private myClass(){} public static Create(string fileName) { // some code... } } There are some places in the .Net framework that use the static method to create instances. At first I was thinking, it registers it's instances to keep track of them, but regular constructors could do the same thing through the use of private static variables. What is the reasoning behind this style?

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  • What reasons are there to place member functions before member variables or vice/versa?

    - by Cory Klein
    Given a class, what reasoning is there for either of the two following code styles? Style A: class Foo { private: doWork(); int bar; } Style B: class Foo { private: int bar; doWork(); } For me, they are a tie. I like Style A because the member variables feel more fine-grained, and thus would appear past the more general member functions. However, I also like Style B, because the member variables seem to determine, in a OOP-style way, what the class is representing. Are there other things worth considering when choosing between these two styles?

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  • What application you recommend to start peeking to learn Python style?

    - by voyager
    Do you know any application, the more interesting/useful the better, to introduce a new person to Python language and the Python code style, but not necessarily to OO programing, so as to learn the subtleties and idioms of the language and surrounding community? I'm thinking along the lines of people that has worked with JavaScript, Java or .NET, and already have a strong hold of OO concepts.

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  • Pyjamas import statements

    - by Gordon Worley
    I'm starting to use Pyjamas and I'm running into some annoyances. I have to import a lot of stuff to make a script work well. For example, to make a button I need to first from pyjamas.ui.Button import Button and then I can use Button. Note that import pyjamas.ui.Button and then using Button.Button doesn't work (results in errors when you build to JavaScript, at least in 0.7pre1). Does anyone have a better example of a good way to do the import statements in Pyjamas than what the Pyjamas folks have on their site? Doing things their way is possible, but ugly and overly complicated from my perspective, especially when you want to use a dozen or more ui components.

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  • Python: When passing variables between methods, is it necessary to assign it a new name?

    - by Anthony
    I'm thinking that the answer is probably 'no' if the program is small and there are a lot of methods, but what about in a larger program? If I am going to be using one variable in multiple methods throughout the program, is it smarter to: Come up with a different phrasing for each method (to eliminate naming conflicts). Use the same name for each method (to eliminate confusion) Just use a global variable (to eliminate both) This is more of a stylistic question than anything else. What naming convention do YOU use when passing variables?

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  • iPhone programming guideline : List / detail / modify

    - by Oliver
    Hello, I have a program that displays a list (a TableView). When the user clicks an item, it's detail is shown. On the detail view, the user can ask to modify it so a modify window is shown. Here, the user can ask to delete the item. I would like at this time return to the list with the item deleted from the list and from the data source. There may be thousands of methods to do this, but I wonder which is the best / good one. Could you help me, and/or give me a good reference to read about this ? Thank you.

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  • How can I configure Xcode to put '{' where I want it in generated files

    - by djhworld
    I know this is a fairly contentious issue amongst programmers, but when developing I like my IDE to position the opening curly bracket underneath the method/interface/control declaration, for illustrative purposes: - This is how Xcode automatically generates skeleton methods with the { at the end: - -(void) isTrue:(BOOL)input { if(input) { return YES; } else { return NO; } } This is how I like to lay out my code (which I believe is called the Allman style): - -(void) isTrue:(BOOL)input { if(input) { return YES; } else { return NO; } } I'm just wondering if there's any configuration switch in Xcode to enable this style of development? It's really annoying when typing out if/else statements as it tends to auto-complete the else clause with the { at the end of the line which just looks silly if you like developing with them underneath. Or am I being unreasonable? Is Objective-C supposed to adhere to a standard defined by Apple?

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  • best practice when referring to a program's name in C

    - by guest
    what is considered best practice when referring to a program's name? i've seen #define PROGRAM_NAME "myprog" printf("this is %s\n", PROGRAM_NAME); as well as printf("this is %s\n", argv[0]); i know, that the second approach will give me ./myprog rather than myprog when the program is not called from $PATH and that the first approach will guarantee consistence regarding the program's name. but is there anything else, that makes one approach superior to the other?

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  • How to convince a colleague that code duplication is bad?

    - by vitaut
    A colleague of mine was implementing a new feature in a project we work on together and he did it by taking a file containing the implementation of a similar feature from the same project, creating a copy of it renaming all the global declarations and slightly modifying the implementation. So we ended up with two large files that are almost identical apart from renaming. I tried to explain that it makes our project more difficult to maintain but he doesn't want to change anything saying that it is easier for him to program in such way and that there is no reason to fix the code if it "ain't broke". How can I convince him that such code duplication is a bad thing? It is related to this questions, but I am more interested in the answers targeted to a technical person (another programmer), for example a reference to an authoritative source like a book would be great. I have already tried simple arguments and haven't succeeded.

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  • A good way to implement useable Callbacks in C++

    - by Marcel J.
    I have a custom Menu class written in C++. To seperate the code into easy-to-read functions I am using Callbacks. Since I don't want to use Singletons for the Host of the Menu I provide another parameter (target) which will be given to the callback as the first parameter (some kind of workaround for the missing "this" reference). Registration-Signature AddItem(string s, void(*callback)(void*,MenuItem*), void* target = NULL) Example of a Registration menu->AddItem(TRANSLATE, "translate", &MyApp::OnModeSelected); Example of a Handler /* static */ void MyApp::OnModeSelected(void* that, MenuItem* item) { MyApp *self = (MyApp*)that; self->activeMode = item->text; } Is there anything one could consider dirty with this approach? Are there maybe better ones?

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  • please help me to find Bug in my Code (segmentation fault)

    - by Vikramaditya Battina
    i am tring to solve this http://www.spoj.com/problems/LEXISORT/ question it working fine in visual studio compiler and IDEone also but when i running in SPOJ compiler it is getting SEGSIGV error Here my code goes #include<stdio.h> #include<stdlib.h> #include<string.h> char *getString(); void lexisort(char **str,int num); void countsort(char **str,int i,int num); int main() { int num_test; int num_strings; char **str; int i,j; scanf("%d",&num_test); for(i=0;i<num_test;i++) { scanf("%d",&num_strings); str=(char **)malloc(sizeof(char *)*num_strings); for(j=0;j<num_strings;j++) { str[j]=(char *)malloc(sizeof(char)*11); scanf("%s",str[j]); } lexisort(str,num_strings); for(j=0;j<num_strings;j++) { printf("%s\n",str[j]); free(str[j]); } free(str); } return 0; } void lexisort(char **str,int num) { int i; for(i=9;i>=0;i--) { countsort(str,i,num); } } void countsort(char **str,int i,int num) { int buff[52]={0,0},k,x; char **temp=(char **)malloc(sizeof(char *)*num); for(k=0;k<52;k++) { buff[k]=0; } for(k=0;k<num;k++) { if(str[k][i]>='A' && str[k][i]<='Z') { buff[(str[k][i]-'A')]++; } else { buff[26+(str[k][i]-'a')]++; } } for(k=1;k<52;k++) { buff[k]=buff[k]+buff[k-1]; } for(k=num-1;k>=0;k--) { if(str[k][i]>='A' && str[k][i]<='Z') { x=buff[(str[k][i]-'A')]; temp[x-1]=str[k]; buff[(str[k][i]-'A')]--; } else { x=buff[26+(str[k][i]-'a')]; temp[x-1]=str[k]; buff[26+(str[k][i]-'a')]--; } } for(k=0;k<num;k++) { str[k]=temp[k]; } free(temp); }

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  • Python Etiquette: Importing Modules

    - by F3AR3DLEGEND
    Say I have two Python modules: module1.py: import module2 def myFunct(): print "called from module1" module2.py: def myFunct(): print "called from module2" def someFunct(): print "also called from module2" If I import module1, is it better etiquette to re-import module2, or just refer to it as module1.module2? For example (someotherfile.py): import module1 module1.myFunct() # prints "called from module1" module1.module2.myFunct() # prints "called from module2" I can also do this: module2 = module1.module2. Now, I can directly call module2.myFunct(). However, I can change module1.py to: from module2 import * def myFunct(): print "called from module1" Now, in someotherfile.py, I can do this: import module1 module1.myFunct() # prints "called from module1"; overrides module2 module1.someFunct() # prints "also called from module2" Also, by importing *, help('module1') shows all of the functions from module2. On the other hand, (assuming module1.py uses import module2), I can do: someotherfile.py: import module1, module2 module1.myFunct() # prints "called from module1" module2.myFunct() # prints "called from module2" Again, which is better etiquette and practice? To import module2 again, or to just refer to module1's importation?

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  • Redundant code constructs

    - by Diomidis Spinellis
    The most egregiously redundant code construct I often see involves using the code sequence if (condition) return true; else return false; instead of simply writing return (condition); I've seen this beginner error in all sorts of languages: from Pascal and C to PHP and Java. What other such constructs would you flag in a code review?

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  • Enum.TryParse with Flags attribute

    - by Sunny
    I have written code to TryParse enum either by value or by its name as shown below. How can I extend this code to include parsing enums with Flags attribute? public static bool TryParse<T>(this T enum_type, object value, out T result) where T : struct { return enum_type.TryParse<T>(value, true, out result); } public static bool TryParse<T>(this T enum_type, object value, bool ignoreCase, out T result) where T : struct { result = default(T); var is_converted = false; var is_valid_value_for_conversion = new Func<T, object, bool, bool>[]{ (e, v, i) => e.GetType().IsEnum, (e, v, i) => value != null, (e, v, i) => Enum.GetNames(e.GetType()).Any(n => String.Compare(n, v.ToString(), i) == 0) || Enum.IsDefined(e.GetType(), v) }; if(is_valid_value_for_conversion.All(rule => rule(enum_type, value, ignoreCase))){ result = (T)Enum.Parse(typeof(T), value.ToString(), ignoreCase); is_converted = true; } return is_converted; } Currently this code works for the following enums: enum SomeEnum{ A, B, C } // can parse either by 'A' or 'a' enum SomeEnum1 : int { A = 1, B = 2, C = 3 } // can parse either by 'A' or 'a' or 1 or "1" Does not work for: [Flags] enum SomeEnum2 { A = 1, B = 2, C = 4 } // can parse either by 'A' or 'a' // cannot parse for A|B Thanks!

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  • How to name variables which are structs

    - by evilpie
    Hello, i often work on private projects using the WinApi, and as you might know, it has thousands of named and typedefed structs like MEMORY_BASIC_INFORMATION. I will stick to this one in my question, what still is preferred, or better when you want to name a variable of this type. Is there some kind of style guide for this case? For example if i need that variable for the VirtualQueryEx function. Some ideas: MEMORY_BASIC_INFORMATION memoryBasicInformation; MEMORY_BASIC_INFORMATION memory_basic_information; Just use the name of the struct non capitalized and with or without the underlines. MEMORY_BASIC_INFORMATION basicInformation; MEMORY_BASIC_INFORMATION information; Short form? MEMORY_BASIC_INFORMATION mbi; I often see this style, using the abbreviation of the struct name. MEMORY_BASIC_INFORMATION buffer; VirtualQueryEx defines the third parameter lpBuffer (where you pass the pointer to the struct), so using this name might be an idea, too. Cheers

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