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• Good functions and techniques for dealing with haskell tuples?

  - by toofarsideways

  I've been doing a lot of work with tuples and lists of tuples recently and I've been wondering if I'm being sensible. Things feel awkward and clunky which for me signals that I'm doing something wrong. For example I've written three convenience functions for getting the first, second and third value in a tuple of 3 values. Is there a better way I'm missing? Are there more general functions that allow you to compose and manipulate tuple data? Here are some things I am trying to do that feel should be generalisable. Extracting values: Do I need to create a version of fst,snd,etc... for tuples of size two, three, four and five, etc...? fst3(x,_,_) = x fst4(x,_,_,_) = x Manipulating values: Can you increment the last value in a list of pairs and then use that same function to increment the last value in a list of triples? Zipping and Unzipping values: There is a zip and a zip3. Do I also need a zip4? or is there some way of creating a general zip function? Sorry if this seems subjective, I honestly don't know if this is even possible or if I'm wasting my time writing 3 extra functions every time I need a general solution. Thank you for any help you can give!

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• Prevent coersion to a single type in unlist() or c(); passing arguments to wrapper functions

  - by Leo Alekseyev

  Is there a simple way to flatten a list while retaining the original types of list constituents?.. Is there a way to programmatically construct a heterogeneous list?.. For instance, I want to create a simple wrapper for functions like png(filename,width,height) that would take device name, file name, and a list of options. The naive approach would be something like my.wrapper <- function(dev,name,opts) { do.call(dev,c(filename=name,opts)) } or similar code with unlist(list(...)). This doesn't work because opts gets coerced to character, and the resulting call is e.g. png(filename,width="500",height="500"). If there's no straightforward way to create heterogeneous lists like that, is there a standard idiomatic way to splice arguments into functions without naming them explicitly (e.g. do.call(dev,list(filename=name,width=opts["width"]))? -- Edit -- Gavin Simpson answered both questions below in his discussion about constructing wrapper functions. Let me give a summary of the answer to the title question: It is possible to construct a heterogeneous list with c() provided the arguments to c() are lists. To wit: > foo <- c("a","b"); bar <- 1:3 > c(foo,bar) [1] "a" "b" "1" "2" "3" > c(list(foo),list(bar)) [[1]] [1] "a" "b" [[2]] [1] 1 2 3 > c(as.list(foo),as.list(bar)) ## this creates a flattened heterogeneous list [[1]] [1] "a" [[2]] [1] "b" [[3]] [1] 1 [[4]] [1] 2 [[5]] [1] 3

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• Is there a PHP refactoring tool to tell what functions are never called?

  - by ae

  I have a large codebase which has suffered many changes over the years. I would like to remove the functions that are no longer called or relevant. Is there a tool that will analysis the codebase and determine if a method is ever used? I'm also using phpunit/xdebug which reports which functions have not been run for the unit tests, however coverage is only at 55% and will require a massive amount of work to bring it up to 100% (I'm working on it!). Anything that was a command line tool would be extra good as I could hook it into hudson (CI).

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• Which functions in the C standard library commonly encourage bad practice?

  - by Ninefingers

  Hello all, This is inspired by this question and the comments on one particular answer in that I learnt that strncpy is not a very safe string handling function in C and that it pads zeros, until it reaches n, something I was unaware of. Specifically, to quote R.. strncpy does not null-terminate, and does null-pad the whole remainder of the destination buffer, which is a huge waste of time. You can work around the former by adding your own null padding, but not the latter. It was never intended for use as a "safe string handling" function, but for working with fixed-size fields in Unix directory tables and database files. snprintf(dest, n, "%s", src) is the only correct "safe strcpy" in standard C, but it's likely to be a lot slower. By the way, truncation in itself can be a major bug and in some cases might lead to privilege elevation or DoS, so throwing "safe" string functions that truncate their output at a problem is not a way to make it "safe" or "secure". Instead, you should ensure that the destination buffer is the right size and simply use strcpy (or better yet, memcpy if you already know the source string length). And from Jonathan Leffler Note that strncat() is even more confusing in its interface than strncpy() - what exactly is that length argument, again? It isn't what you'd expect based on what you supply strncpy() etc - so it is more error prone even than strncpy(). For copying strings around, I'm increasingly of the opinion that there is a strong argument that you only need memmove() because you always know all the sizes ahead of time and make sure there's enough space ahead of time. Use memmove() in preference to any of strcpy(), strcat(), strncpy(), strncat(), memcpy(). So, I'm clearly a little rusty on the C standard library. Therefore, I'd like to pose the question: What C standard library functions are used inappropriately/in ways that may cause/lead to security problems/code defects/inefficiencies? In the interests of objectivity, I have a number of criteria for an answer: Please, if you can, cite design reasons behind the function in question i.e. its intended purpose. Please highlight the misuse to which the code is currently put. Please state why that misuse may lead towards a problem. I know that should be obvious but it prevents soft answers. Please avoid: Debates over naming conventions of functions (except where this unequivocably causes confusion). "I prefer x over y" - preference is ok, we all have them but I'm interested in actual unexpected side effects and how to guard against them. As this is likely to be considered subjective and has no definite answer I'm flagging for community wiki straight away. I am also working as per C99.

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• SQLAlchemy session management in long-running process

  - by codeape

  Scenario: A .NET-based application server (Wonderware IAS/System Platform) hosts automation objects that communicate with various equipment on the factory floor. CPython is hosted inside this application server (using Python for .NET). The automation objects have scripting functionality built-in (using a custom, .NET-based language). These scripts call Python functions. The Python functions are part of a system to track Work-In-Progress on the factory floor. The purpose of the system is to track the produced widgets along the process, ensure that the widgets go through the process in the correct order, and check that certain conditions are met along the process. The widget production history and widget state is stored in a relational database, this is where SQLAlchemy plays its part. For example, when a widget passes a scanner, the automation software triggers the following script (written in the application server's custom scripting language): ' wiget_id and scanner_id provided by automation object ' ExecFunction() takes care of calling a CPython function retval = ExecFunction("WidgetScanned", widget_id, scanner_id); ' if the python function raises an Exception, ErrorOccured will be true ' in this case, any errors should cause the production line to stop. if (retval.ErrorOccured) then ProductionLine.Running = False; InformationBoard.DisplayText = "ERROR: " + retval.Exception.Message; InformationBoard.SoundAlarm = True end if; The script calls the WidgetScanned python function: # pywip/functions.py from pywip.database import session from pywip.model import Widget, WidgetHistoryItem from pywip import validation, StatusMessage from datetime import datetime def WidgetScanned(widget_id, scanner_id): widget = session.query(Widget).get(widget_id) validation.validate_widget_passed_scanner(widget, scanner) # raises exception on error widget.history.append(WidgetHistoryItem(timestamp=datetime.now(), action=u"SCANNED", scanner_id=scanner_id)) widget.last_scanner = scanner_id widget.last_update = datetime.now() return StatusMessage("OK") # ... there are a dozen similar functions My question is: How do I best manage SQLAlchemy sessions in this scenario? The application server is a long-running process, typically running months between restarts. The application server is single-threaded. Currently, I do it the following way: I apply a decorator to the functions I make avaliable to the application server: # pywip/iasfunctions.py from pywip import functions def ias_session_handling(func): def _ias_session_handling(*args, **kwargs): try: retval = func(*args, **kwargs) session.commit() return retval except: session.rollback() raise return _ias_session_handling # ... actually I populate this module with decorated versions of all the functions in pywip.functions dynamically WidgetScanned = ias_session_handling(functions.WidgetScanned) Question: Is the decorator above suitable for handling sessions in a long-running process? Should I call session.remove()? The SQLAlchemy session object is a scoped session: # pywip/database.py from sqlalchemy.orm import scoped_session, sessionmaker session = scoped_session(sessionmaker()) I want to keep the session management out of the basic functions. For two reasons: There is another family of functions, sequence functions. The sequence functions call several of the basic functions. One sequence function should equal one database transaction. I need to be able to use the library from other environments. a) From a TurboGears web application. In that case, session management is done by TurboGears. b) From an IPython shell. In that case, commit/rollback will be explicit. (I am truly sorry for the long question. But I felt I needed to explain the scenario. Perhaps not necessary?)

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• How do I define functions using PLT Scheme macros?

  - by nickname

  I am trying to write a macro that defines a special class of data structure with associated functions. I know this is possible; it is done multiple times in the core language itself. As a specific example, how would I define the define-struct macro in Scheme itself. It needs to create make-struct, struct-<<field>>, etc functions. I tried doing this using define, however, this only defines the function in the macro's lexical scope. How can I actually define a function in a macro?

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• How do I refactor these two C# functions to abstrtact their logic from the specific class properties

  - by ObligatoryMoniker

  I have two functions whose underlying logic is the same but in one case it sets one property value on a class and in another case it sets a different one. How can I rewrite the following two functions to abstract away as much of the algorithm as possible so that I can make changes in logic in a single place? SetBillingAddress private void SetBillingAddress(OrderAddress newBillingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldBillingAddress = basketHelper.Basket.Addresses[basketHelper.BillingAddressID]; bool NewBillingAddressIsNotOldBillingAddress = ((oldBillingAddress == null) || (newBillingAddress.OrderAddressId != oldBillingAddress.OrderAddressId)); bool BillingAddressHasBeenPreviouslySet = (oldBillingAddress != null); bool BillingAddressIsNotSameAsShippingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewBillingAddressIsNotShippingAddress = (newBillingAddress.OrderAddressId != basketHelper.ShippingAddressID); if (NewBillingAddressIsNotOldBillingAddress && BillingAddressHasBeenPreviouslySet && BillingAddressIsNotSameAsShippingAddress) { basketHelper.Basket.Addresses.Remove(oldBillingAddress); } if (NewBillingAddressIsNotOldBillingAddress && NewBillingAddressIsNotShippingAddress) { basketHelper.Basket.Addresses.Add(newBillingAddress); } basketHelper.BillingAddressID = newBillingAddress.OrderAddressId; basketHelper.Basket.Save(); } And here is the second one: SetShippingAddress private void SetBillingAddress(OrderAddress newShippingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldShippingAddress = basketHelper.Basket.Addresses[basketHelper.ShippingAddressID]; bool NewShippingAddressIsNotOldShippingAddress = ((oldShippingAddress == null) || (newShippingAddress.OrderAddressId != oldShippingAddress.OrderAddressId)); bool ShippingAddressHasBeenPreviouslySet = (oldShippingAddress != null); bool ShippingAddressIsNotSameAsBillingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewShippingAddressIsNotBillingAddress = (newShippingAddress.OrderAddressId != basketHelper.BillingAddressID); if (NewShippingAddressIsNotOldShippingAddress && ShippingAddressHasBeenPreviouslySet && ShippingAddressIsNotSameAsBillingAddress) { basketHelper.Basket.Addresses.Remove(oldShippingAddress); } if (NewShippingAddressIsNotOldShippingAddress && NewShippingAddressIsNotBillingAddress) { basketHelper.Basket.Addresses.Add(newShippingAddress); } basketHelper.ShippingAddressID = newShippingAddress.OrderAddressId; basketHelper.Basket.Save(); } My initial thought was that if I could pass a class's property by refernce then I could rewrite the previous functions into something like private void SetPurchaseOrderAddress(OrderAddress newAddress, ref String CurrentChangingAddressIDProperty) and then call this function and pass in either basketHelper.BillingAddressID or basketHelper.ShippingAddressID as CurrentChangingAddressIDProperty but since I can't pass C# properties by reference I am not sure what to do with this code to be able to reuse the logic in both places. Thanks for any insight you can give me.

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• Is it good practice to call module functions directly in VB.NET?

  - by froadie

  I have a Util module in my VB.NET program that has project-wide methods such as logging and property parsing. The general practice where I work seems to be to call these methods directly without prefixing them with Util. When I was new to VB, it took me a while to figure out where these methods/functions were coming from. As I use my own Util methods now, I can't help thinking that it's a lot clearer and more understandable to add Util. before each method call (you know immediately that it's user-defined but not within the current class, and where to find it), and is hardly even longer. What's the general practice when calling procedures/functions of VB modules? Should we prefix them with the module name or not?

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• How do I use theme preprocessor functions for my own templates?

  - by Jergason

  I have several .tpl.php files for nodes, CCK fields, and Views theming. These template files have a lot of logic in them to move things around, strip links, create new links, etc. I understand that this is bad development and not "The Drupal Way". If I understand correctly, "The Drupal Way" is to use preprocessor functions in your template.php file to manipulate variables and add new variables. A few questions about that: Is there a naming convention for creating a preprocessor function for a specific theme? For example, if I have a CCK field template called content-field-field_transmission_make_model.tpl, how would I name the preprocessor function? Can I use template preprocessor functions for node templates, CCK field templates, and Views templates? Do they have different methods of modifying template variables or adding new ones?

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• How do I generate different yyparse functions from lex/yacc for use in the same program?

  - by th

  Hi, I want to generate two separate parsing functions from lex/yacc. Normally yacc gives you a function yyparse() that you can call when you need to do some parsing, but I need to have several different yyparses each associated with different lexers and grammars. The man page seems to suggest the -p (prefix) flag, but this didn't work for me. I got errors from gcc that indicated that yylval was not properly being relabeled (i.e. it claims that several different tokens are not defined). Does anyone know the general rpocedure for generating these separate functions? thanks

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• How do I refactor these two C# functions to abstract their logic from the specific class properties

  - by ObligatoryMoniker

  I have two functions whose underlying logic is the same but in one case it sets one property value on a class and in another case it sets a different one. How can I rewrite the following two functions to abstract away as much of the algorithm as possible so that I can make changes in logic in a single place? SetBillingAddress private void SetBillingAddress(OrderAddress newBillingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldBillingAddress = basketHelper.Basket.Addresses[basketHelper.BillingAddressID]; bool NewBillingAddressIsNotOldBillingAddress = ((oldBillingAddress == null) || (newBillingAddress.OrderAddressId != oldBillingAddress.OrderAddressId)); bool BillingAddressHasBeenPreviouslySet = (oldBillingAddress != null); bool BillingAddressIsNotSameAsShippingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewBillingAddressIsNotShippingAddress = (newBillingAddress.OrderAddressId != basketHelper.ShippingAddressID); if (NewBillingAddressIsNotOldBillingAddress && BillingAddressHasBeenPreviouslySet && BillingAddressIsNotSameAsShippingAddress) { basketHelper.Basket.Addresses.Remove(oldBillingAddress); } if (NewBillingAddressIsNotOldBillingAddress && NewBillingAddressIsNotShippingAddress) { basketHelper.Basket.Addresses.Add(newBillingAddress); } basketHelper.BillingAddressID = newBillingAddress.OrderAddressId; basketHelper.Basket.Save(); } And here is the second one: SetShippingAddress private void SetBillingAddress(OrderAddress newShippingAddress) { BasketHelper basketHelper = new BasketHelper(SiteConstants.BasketName); OrderAddress oldShippingAddress = basketHelper.Basket.Addresses[basketHelper.ShippingAddressID]; bool NewShippingAddressIsNotOldShippingAddress = ((oldShippingAddress == null) || (newShippingAddress.OrderAddressId != oldShippingAddress.OrderAddressId)); bool ShippingAddressHasBeenPreviouslySet = (oldShippingAddress != null); bool ShippingAddressIsNotSameAsBillingAddress = (basketHelper.ShippingAddressID != basketHelper.BillingAddressID); bool NewShippingAddressIsNotBillingAddress = (newShippingAddress.OrderAddressId != basketHelper.BillingAddressID); if (NewShippingAddressIsNotOldShippingAddress && ShippingAddressHasBeenPreviouslySet && ShippingAddressIsNotSameAsBillingAddress) { basketHelper.Basket.Addresses.Remove(oldShippingAddress); } if (NewShippingAddressIsNotOldShippingAddress && NewShippingAddressIsNotBillingAddress) { basketHelper.Basket.Addresses.Add(newShippingAddress); } basketHelper.ShippingAddressID = newShippingAddress.OrderAddressId; basketHelper.Basket.Save(); } My initial thought was that if I could pass a class's property by refernce then I could rewrite the previous functions into something like private void SetPurchaseOrderAddress(OrderAddress newAddress, ref String CurrentChangingAddressIDProperty) and then call this function and pass in either basketHelper.BillingAddressID or basketHelper.ShippingAddressID as CurrentChangingAddressIDProperty but since I can't pass C# properties by reference I am not sure what to do with this code to be able to reuse the logic in both places. Thanks for any insight you can give me.

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• Is it safe to use the same parameters for input and output in D3DX functions?

  - by JB

  Using the D3DX library that is a part of directX, specifically directx9 in this case, I'm wondering if it's safe to use the same matrix (or vector etc) for input and ouput D3DXMATRIX mat; D3DXMatrixInverse(&mat, NULL, &mat); I've been avoiding doing so, assuming that it would result in bad things happening when parts of the array got partly overwritten as results are calculated but I see an awful lot of code around that does exactly this. A brief test indicates that it seems to work ok, so I'm assuming that the D3DX functions take a copy where necessary of the input data, or some other method to ensure that this works ok, but I can't find it documented anywhere so I'm reluctant to rely on it working. Is there any official statement on using the functions like this?

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• Why Microsoft not provide for C# a static Win32 class with the most native functions and structures

  - by Oleg

  Everybody who used P/Invoke of Windows API knows a long list of declarations of static functions with attributes like [DllImport ("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)] The declaration of structures copied from Windows headers like WinNT.h or from web sites like www.pinvoke.net take also a lot of place in our programs. Why we all have to spend our time for this? Why Microsoft not give us a simple way to include a line like in old unmanaged programs #include <windows.h> and we would be have access to a static class Native with all or the most Windows functions and structures inside?

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• How can I call some javascript functions but, waiting for the previous has finished?

  - by texai

  I want to call some functions but waiting for the previous one has finished. I know jQuery provides a callback argument in several functions, but I want to learn how implement this behaviour in my own jQuery plugin. So this is the case: After read answers from my previous question I wrote this: (function(callback){ $('#art1').animate({'width':'1000px'},1000); callback(); })((function(callback2){ $('#art2').animate({'width':'1000px'},1000); callback2(); })(function(){ $('#art3').animate({'width':'1000px'},1000); })); But still not working. Three animates still starting at same time. I want they were called one after other. But without using: $('#art1').animate({'width':'1000px'},1000,'linear',function(){ $('#art2').animate({'width':'1000px'},1000,'linear',function(){ $('#art3').animate({'width':'1000px'},1000); }); });

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• Is there a consolidated way of writing several prototype functions for a single object?

  - by Christopher Altman

  I have about eight prototype functions for the Date object. I would like to avoid repeating Date.prototype. Is there a consolidated way of writing several prototype functions for a single object? I tried this to no avail: Date.prototype = { getMonthText: function(date){ var month = this.getMonth(); if(month==12) month = 0; return ['JAN','FEB','MAR','APR','MAY','JUN','JUL','AUG','SEP','OCT','NOV','DEC'][month]; }, getDaysInMonth: function(date){ return 32 - new Date(this.getFullYear(), this.getMonth(), 32).getDate(); } };

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• In Java ,where in memory are class functions put?

  - by husain

  In java ,where in memory are class functions put?

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• C++ vector of strings, pointers to functions, and the resulting frustration.

  - by Kyle

  So I am a first year computer science student, for on of my final projects, I need to write a program that takes a vector of strings, and applies various functions to these. Unfortunately, I am really confused on how to use pointer to pass the vector from function to function. Below is some sample code to give an idea of what I am talking about. I also get an error message when I try to deference any pointer. thanks. #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; vector<string>::pointer function_1(vector<string>::pointer ptr); void function_2(vector<string>::pointer ptr); int main() { vector<string>::pointer ptr; vector<string> svector; ptr = &svector[0]; function_1(ptr); function_2(ptr); } vector<string>::pointer function_1(vector<string>::pointer ptr) { string line; for(int i = 0; i < 10; i++) { cout << "enter some input ! \n"; // i need to be able to pass a reference of the vector getline(cin, line); // through various functions, and have the results *ptr.pushback(line); // reflectedin main(). But I cannot use member functions } // of vector with a deferenced pointer. return(ptr); } void function_2(vector<string>::pointer ptr) { for(int i = 0; i < 10; i++) { cout << *ptr[i] << endl; } }

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• OOP question about functions that struck me all of a sudden.

  - by Nitesh Panchal

  Hello, May be my question is stupid. But i would like to get it cleared. We know that functions are loaded in memory only once and when you create new objects, only instance variables gets created, functions are never created. My question is, say suppose there is server and all clients access a method named createCustomer(). Say suppose all clients do something which fired createCustomer on server. So, if the method is in middle of execution and new client fires it. Will the new request be put on wait? or new request also will start executing the method? How does it all get managed when there is only one copy of function in memory? No book mentions answers to this type of questions. So i am posting here where i am bound to get answers :).

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• Move email off Small Business Server to Google Apps, retain other SBS functions?

  - by Paul S.

  Recently, an in-house Microsoft Small Business Server 2011 was installed where I work. Unfortunately, our buildings have a bad electrical power supply and we suffer frequent outages. We have a large percentage of staff working off-site. Now when the power goes off here, everyone everywhere loses email functionality. I have been assigned to research the possibility of routing our email to Google Apps while maintaining LAN functions on the SBS. I haven't worked with Microsoft products for several years now, so do not know how SBS is structured. Can anyone here tell me if this is possible, or point me to good resources that explain our options?

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• Where is the rand php function located? localhost php running, path of default functions?

  - by Bona Chon

  I have a local server installed on my Mac (MAMP). My question is, where I can find the php functions in my computer? What is the path to the functions folder? For instance, rand() time() isset() explode(). I would like to se the code to learn of it. I have a while looking for it, but I can't find it. Or is it that is already compiled? Can someone help me here? I'm kind of lost. Thanks people. EDIT: can you be a little bit more positive? I;m trying to learn here, forgive me if I'm not to smart for you. Thanks again. Explanations would help better than giving links I guess?

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• Can we use wmain() functions with Unix compilers or it'll work only on windows?

  - by Ole Jak

  Can we use wmain() functions with Unix compilers (git) or it'll work only on\for windows?

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• Learning Python Basics

  - by StaticExtasy

  So I'm trying to learn python better and i've been using this website http://www.learnpython.org/ I'm on to functions right now, heres the code #Add your functions here (before the existing functions) def list_benefits(): myList = ['More organized code','More readable code','Easier code reuse','Allowing programmers to share and connect code together'] return myList def build_sentence(info): addMe = " is a benefit of functions!" for i in info: meInfo = i + addMe return meInfo def name_the_benefits_of_functions(): list_of_benefits = list_benefits() for benefit in list_of_benefits: print build_sentence(benefit) name_the_benefits_of_functions() the output being e is a benefit of functions! e is a benefit of functions! e is a benefit of functions! r is a benefit of functions! What am i missing to return the whole scentence

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• JavaScript Class Patterns

  - by Liam McLennan

  To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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• JavaScript Class Patterns

  - by Liam McLennan

  To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var john = new Person("John Galt", 50); console.log(john.toString()); var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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• Solaris 11.2: Functional Deprecation

  - by alanc

  In Solaris 11.1, I updated the system headers to enable use of several attributes on functions, including noreturn and printf format, to give compilers and static analyzers more information about how they are used to give better warnings when building code. In Solaris 11.2, I've gone back in and added one more attribute to a number of functions in the system headers: __attribute__((__deprecated__)). This is used to warn people building software that they’re using function calls we recommend no longer be used. While in many cases the Solaris Binary Compatibility Guarantee means we won't ever remove these functions from the system libraries, we still want to discourage their use. I made passes through both the POSIX and C standards, and some of the Solaris architecture review cases to come up with an initial list which the Solaris architecture review committee accepted to start with. This set is by no means a complete list of Obsolete function interfaces, but should be a reasonable start at functions that are well documented as deprecated and seem useful to warn developers away from. More functions may be flagged in the future as they get deprecated, or if further passes are made through our existing deprecated functions to flag more of them. Header Interface Deprecated by Alternative Documented in <door.h> door_cred(3C) PSARC/2002/188 door_ucred(3C) door_cred(3C) <kvm.h> kvm_read(3KVM), kvm_write(3KVM) PSARC/1995/186 Functions on kvm_kread(3KVM) man page kvm_read(3KVM) <stdio.h> gets(3C) ISO C99 TC3 (Removed in ISO C11), POSIX:2008/XPG7/Unix08 fgets(3C) gets(3C) man page, and just about every gets(3C) reference online from the past 25 years, since the Morris worm proved bad things happen when it’s used. <unistd.h> vfork(2) PSARC/2004/760, POSIX:2001/XPG6/Unix03 (Removed in POSIX:2008/XPG7/Unix08) posix_spawn(3C) vfork(2) man page. <utmp.h> All functions from getutent(3C) man page PSARC/1999/103 utmpx functions from getutentx(3C) man page getutent(3C) man page <varargs.h> varargs.h version of va_list typedef ANSI/ISO C89 standard <stdarg.h> varargs(3EXT) <volmgt.h> All functions PSARC/2005/672 hal(5) API volmgt_check(3VOLMGT), etc. <sys/nvpair.h> nvlist_add_boolean(3NVPAIR), nvlist_lookup_boolean(3NVPAIR) PSARC/2003/587 nvlist_add_boolean_value, nvlist_lookup_boolean_value nvlist_add_boolean(3NVPAIR) & (9F), nvlist_lookup_boolean(3NVPAIR) & (9F). <sys/processor.h> gethomelgroup(3C) PSARC/2003/034 lgrp_home(3LGRP) gethomelgroup(3C) <sys/stat_impl.h> _fxstat, _xstat, _lxstat, _xmknod PSARC/2009/657 stat(2) old functions are undocumented remains of SVR3/COFF compatibility support If the above table is cut off when viewing in the blog, try viewing this standalone copy of the table. To See or Not To See To see these warnings, you will need to be building with either gcc (versions 3.4, 4.5, 4.7, & 4.8 are available in the 11.2 package repo), or with Oracle Solaris Studio 12.4 or later (which like Solaris 11.2, is currently in beta testing). For instance, take this oversimplified (and obviously buggy) implementation of the cat command: #include <stdio.h> int main(int argc, char **argv) { char buf[80]; while (gets(buf) != NULL) puts(buf); return 0; } Compiling it with the Studio 12.4 beta compiler will produce warnings such as: % cc -V cc: Sun C 5.13 SunOS_i386 Beta 2014/03/11 % cc gets_test.c "gets_test.c", line 6: warning: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 The exact warning given varies by compilers, and the compilers also have a variety of flags to either raise the warnings to errors, or silence them. Of couse, the exact form of the output is Not An Interface that can be relied on for automated parsing, just shown for example. gets(3C) is actually a special case — as noted above, it is no longer part of the C Standard Library in the C11 standard, so when compiling in C11 mode (i.e. when __STDC_VERSION__ >= 201112L), the <stdio.h> header will not provide a prototype for it, causing the compiler to complain it is unknown: % gcc -std=c11 gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration] while (gets(buf) != NULL) ^ The gets(3C) function of course is still in libc, so if you ignore the error or provide your own prototype, you can still build code that calls it, you just have to acknowledge you’re taking on the risk of doing so yourself. Solaris Studio 12.4 Beta % cc gets_test.c "gets_test.c", line 6: warning: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 % cc -errwarn=E_DEPRECATED_ATT gets_test.c "gets_test.c", line 6: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 cc: acomp failed for gets_test.c This warning is silenced in the 12.4 beta by cc -erroff=E_DEPRECATED_ATT No warning is currently issued by Studio 12.3 & earler releases. gcc 3.4.3 % /usr/sfw/bin/gcc gets_test.c gets_test.c: In function `main': gets_test.c:6: warning: `gets' is deprecated (declared at /usr/include/iso/stdio_iso.h:221) Warning is completely silenced with gcc -Wno-deprecated-declarations gcc 4.7.3 % /usr/gcc/4.7/bin/gcc gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Wdeprecated-declarations] % /usr/gcc/4.7/bin/gcc -Werror=deprecated-declarations gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: error: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Werror=deprecated-declarations] cc1: some warnings being treated as errors Warning is completely silenced with gcc -Wno-deprecated-declarations gcc 4.8.2 % /usr/bin/gcc gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Wdeprecated-declarations] while (gets(buf) != NULL) ^ % /usr/bin/gcc -Werror=deprecated-declarations gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: error: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Werror=deprecated-declarations] while (gets(buf) != NULL) ^ cc1: some warnings being treated as errors Warning is completely silenced with gcc -Wno-deprecated-declarations

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