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  • What can I do with dynamic typing that I can not do with static typing

    - by Justin984
    I've been using python for a few days now and I think I understand the difference between dynamic and static typing. What I don't understand is why it's useful. I keep hearing about its "flexibility" but it seems like it just moves a bunch of compile time checks to runtime, which means more unit tests. This seems like an awfully big tradeoff to make for small advantages like readability and "flexibility". Can someone provide me with a real world example where dynamic typing allows me to do something I can't do with static typing?

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  • What functionality does dynamic typing allow?

    - by Justin984
    I've been using python for a few days now and I think I understand the difference between dynamic and static typing. What I don't understand is under what circumstances it would be preferred. It is flexible and readable, but at the expense of more runtime checks and additional required unit testing. Aside from non-functional criteria like flexibility and readability, what reasons are there to choose dynamic typing? What can I do with dynamic typing that isn't possible otherwise? What specific code example can you think of that illustrates a concrete advantage of dynamic typing?

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  • Is duck typing a subset of polymorphism

    - by Raynos
    From Polymorphism on WIkipedia In computer science, polymorphism is a programming language feature that allows values of different data types to be handled using a uniform interface. From duck typing on Wikipedia In computer programming with object-oriented programming languages, duck typing is a style of dynamic typing in which an object's current set of methods and properties determines the valid semantics, rather than its inheritance from a particular class or implementation of a specific interface. My interpretation is that based on duck typing, the objects methods/properties determine the valid semantics. Meaning that the objects current shape determines the interface it upholds. From polymorphism you can say a function is polymorphic if it accepts multiple different data types as long as they uphold an interface. So if a function can duck type, it can accept multiple different data types and operate on them as long as those data types have the correct methods/properties and thus uphold the interface. (Usage of the term interface is meant not as a code construct but more as a descriptive, documenting construct) What is the correct relationship between ducktyping and polymorphism ? If a language can duck type, does it mean it can do polymorphism ?

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  • Python Forgiveness vs. Permission and Duck Typing

    - by darkfeline
    In Python, I often hear that it is better to "beg forgiveness" (exception catching) instead of "ask permission" (type/condition checking). In regards to enforcing duck typing in Python, is this try: x = foo.bar except AttributeError: pass else: do(x) better or worse than if hasattr(foo, "bar"): do(foo.bar) else: pass in terms of performance, readability, "pythonic", or some other important factor?

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  • What is the best keyboard for typing speed (not layouts)

    - by Gapton
    So I am a programmer, and I like playing typing speed games. My typing speed is, for common English words, 85 to 90 wpm, max 95. I type on various devices, my laptop, desktop, office pc.... they all have slightly different keyboards. Being a curious programmer, I wonder what types of keyboard is used for the highest possible typing speed. Or let me phrase it in another way, what is the type of keyboards that people use in typing speed contest? Here is something I know that I feel like I can share: It must be a wired keyboard, I can feel the lag as I am typing this on my wireless keyboard, even if it is a slightly more expensive model which claims to have zero lag. I know people prefer a mechanical keyboard, for the hepatic feedback, however I have not tried one. It lasts longer and is noisy, it also does not have the problem of normal keyboards where you press many keys at a time the signals will get all jammed and the computer will only receive one or two keys. I personally prefer those "thin profile" keyboards. I type a lot, and 95 wpm put me in the top 5%, this is of course just on a gaming site. However when I type on the fat keyboards, my fingers have to travel a much longer distance before the keys actually click. This is where I find myself typing much faster with those thin profile keyboards found on my laptop. Because my fingers only hover on the keys and I only need to press a short distance, each stroke takes less force and light rapid strokes is what makes me type fast. When I type on a fat keyboard, I was forced to use heavy strokes, and this slows me down. There must be some people out there who are keyboard scientists, who actually do experiments and user tests with different setups. It would be interesting to understand more about the things we use everyday for not just work but a majority of our communications. P.S. this is about hardware and not about switching keyboard layouts to dvorak

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  • Static/Dynamic vs Strong/Weak

    - by Dan Revell
    I see these terms banded around all over the place in programming and I have a vague notion of what they mean. A search shows me that such things have been asked all over stack overflow in fact. As far as I'm aware Static/Dynamic typing in languages is subtly different to Strong/Weak typing but what that difference is eludes me. Different sources seem to use different different meanings or even use the terms interchangeably. I can't find somewhere that talks about both and actually spells out the difference. What would be nice is if someone could please spell this out clearly here for me and the rest of the world.

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  • Simulating aspects of static-typing in a duck-typed language

    - by Mike
    In my current job I'm building a suite of Perl scripts that depend heavily on objects. (using Perl's bless() on a Hash to get as close to OO as possible) Now, for lack of a better way of putting this, most programmers at my company aren't very smart. Worse, they don't like reading documentation and seem to have a problem understanding other people's code. Cowboy coding is the game here. Whenever they encounter a problem and try to fix it, they come up with a horrendous solution that actually solves nothing and usually makes it worse. This results in me, frankly, not trusting them with code written in duck typed language. As an example, I see too many problems with them not getting an explicit error for misusing objects. For instance, if type A has member foo, and they do something like, instance->goo, they aren't going to see the problem immediately. It will return a null/undefined value, and they will probably waste an hour finding the cause. Then end up changing something else because they didn't properly identify the original problem. So I'm brainstorming for a way to keep my scripting language (its rapid development is an advantage) but give an explicit error message when an an object isn't used properly. I realize that since there isn't a compile stage or static typing, the error will have to be at run time. I'm fine with this, so long as the user gets a very explicit notice saying "this object doesn't have X" As part of my solution, I don't want it to be required that they check if a method/variable exists before trying to use it. Even though my work is in Perl, I think this can be language agnostic.

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  • Is there a compiled* programming language with dynamic, maybe even weak typing?

    - by sub
    I wondered if there is a programming language which compiles to machine code/binary (not bytecode then executed by a VM, that's something completely different when considering typing) that features dynamic and/or weak typing, e.g: Think of a compiled language where: Variables don't need to be declared Variables can be created doing runtime Functions can return values of different types Questions: Is there such a programming language? (Why) not? I think that a dynamically yet strong typed, compiled language would really sense, but is it possible?

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  • Which tips helped you learn touch-typing? [closed]

    - by julien
    I've been learning touch-typing for about two weeks now, and I'm really commited to mastering this skill. Eventhough I'm doing ok with prose already, I'm struggling with programming syntax and even more with keybindings. Those stray you away from the home row more than regular words, and aren't as easy to practice. So I often hunt and peck in order to just get it out, but when reverting to old habits like this, I find it hard to get back into the touch-typing mindframe quickly. One little trick that has helped me so far when getting lost is to reposition every finger on its home row key, and mentally visualize the layout bias of the keyboard, ie the backslash kind of alignment of key columns. It's hard to describe though and probably a bit weird... Hope you guys have better tips !

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  • How can i find touch typing lesson for words with middle row only

    - by user1838032
    I am learning touch typing. i want practice step by step. Is there any site where i can have the options of the keys to select and then have lesson for those slected keys only. I means i select the keys from keyboard and then system prepares the lesson for only those keys with random combination. Current i want to practice keys asdf gh jkl; Now i am not able to find practice for that whole row only. i mena random combinatins

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  • Does weak typing offer any advantages?

    - by sub
    Don't confuse this with static vs. dynamic typing! You all know JavaScripts/PHPs infamous type systems: PHP example: echo "123abc"+2; // 125 - the reason for this is explained // in the PHP docs but still: This hurts echo "4"+1; // 5 - Oh please echo "ABC"*5; // 0 - WTF // That's too much, seriously now. // This here might be actually a use for weak typing, but no - // it has to output garbage. JavaScript example: // A good old JavaScript, maybe you'll do better? alert("4"+1); // 51 - Oh come on. alert("abc"*3); // NaN - What the... // Have your creators ever heard of the word "consistence"? Python example: # Python's type system is actually a mix # It spits errors on senseless things like the first example below AND # allows intelligent actions like the second example. >>> print("abc"+1) Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> print("abc"+1) TypeError: Can't convert 'int' object to str implicitly >>> print("abc"*5) abcabcabcabcabc Ruby example: puts 4+"1" // Type error - as supposed puts "abc"*4 // abcabcabcabc - makes sense After these examples it should be clear that PHP/JavaScript probably have the most inconsistent type systems out there. This is a fact and really not subjective. Now when having a closer look at the type systems of Ruby and Python it seems like they are having a much more intelligent and consistent type system. I think these examples weren't really necessary as we all know that PHP/JavaScript have a weak and Python/Ruby have a strong type system. I just wanted to mention why I'm asking this. Now I have two questions: When looking at those examples, what are the advantages of PHPs and JavaScripts type systems? I can only find downsides: They are inconsistent and I think we know that this is not good Types conversions are hardly controllable Bugs are more likely to happen and much harder to spot Do you prefer one of the both systems? Why? Personally I have worked with PHP, JavaScript and Python so far and must say that Pythons type system has really only advantages over PHPs and JavaScripts. Does anybody here not think so? Why then?

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  • What's an example of duck typing in Java?

    - by Cuga
    I just recently heard of duck typing and I read the Wikipedia article about it, but I'm having a hard time translating the examples into Java, which would really help my understanding. Would anyone be able to give a clear example of duck typing in Java and how I might possibly use it?

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  • Most Up-To-Date C# Duck-Typing Library

    - by Anton Gogolev
    The title says it all, basically. What is the current state of the art on duck typing for C# below version 4.0? I know about Duck Typing Project, I know that BLTookit has something to that end, but I'd like to know if I'm missing something really wicked apart from DLR languages and C# 4.0. The inevitable:

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  • Duck type testing with C# 4 for dynamic objects.

    - by Tracker1
    I'm wanting to have a simple duck typing example in C# using dynamic objects. It would seem to me, that a dynamic object should have HasValue/HasProperty/HasMethod methods with a single string parameter for the name of the value, property, or method you are looking for before trying to run against it. I'm trying to avoid try/catch blocks, and deeper reflection if possible. It just seems to be a common practice for duck typing in dynamic languages (JS, Ruby, Python etc.) that is to test for a property/method before trying to use it, then falling back to a default, or throwing a controlled exception. The example below is basically what I want to accomplish. If the methods described above don't exist, does anyone have premade extension methods for dynamic that will do this? Example: In JavaScript I can test for a method on an object fairly easily. //JavaScript function quack(duck) { if (duck && typeof duck.quack === "function") { return duck.quack(); } return null; //nothing to return, not a duck } How would I do the same in C#? //C# 4 dynamic Quack(dynamic duck) { //how do I test that the duck is not null, //and has a quack method? //if it doesn't quack, return null }

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  • what is duck typing?

    - by ashish yadav
    I recently read an article about duck-typing.It said about calling functions of different classes using object of any class. Is it true?And how will the compiler do it on runtime? I apologize if i am not clear.But it really fascinates me , if we could do it dynamically. So if u people got any idea.I am all ears. thank you!! how will the function be accessed by object of any other class. that violates the basic principle of OOP.and that too dynamically during runtime. And is this feature possible in case of OOP languages?

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  • Does C# have an equivalent to Scala's structural typing?

    - by Tom Morris
    In Scala, I can define structural types as follows: type Pressable { def press(): Unit } This means that I can define a function or method which takes as an argument something that is Pressable, like this: def foo(i: Pressable) { // etc. The object which I pass to this function must have defined for it a method called press() that matches the type signature defined in the type - takes no arguments, returns Unit (Scala's version of void). I can even use the structural type inline: def foo(i: { def press(): Unit }) { // etc. It basically allows the programmer to have all the benefits of duck typing while still having the benefit of compile-time type checking. Does C# have something similar? I've Googled but can't find anything, but I'm not familiar with C# in any depth. If there aren't, are there any plans to add this?

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  • Duck checker in Python: does one exist?

    - by elliot42
    Python uses duck-typing, rather than static type checking. But many of the same concerns ultimately apply: does an object have the desired methods and attributes? Do those attributes have valid, in-range values? Whether you're writing constraints in code, or writing test cases, or validating user input, or just debugging, inevitably somewhere you'll need to verify that an object is still in a proper state--that it still "looks like a duck" and "quacks like a duck." In statically typed languages you can simply declare "int x", and anytime you create or mutate x, it will always be a valid int. It seems feasible to decorate a Python object to ensure that it is valid under certain constraints, and that every time that object is mutated it is still valid under those constraints. Ideally there would be a simple declarative syntax to express "hasattr length and length is non-negative" (not in those words. Not unlike Rails validators, but less human-language and more programming-language). You could think of this as ad-hoc interface/type system, or you could think of it as an ever-present object-level unit test. Does such a library exist to declare and validate constraint/duck-checking on Python-objects? Is this an unreasonable tool to want? :) (Thanks!) Contrived example: rectangle = {'length': 5, 'width': 10} # We live in a fictional universe where multiplication is super expensive. # Therefore any time we multiply, we need to cache the results. def area(rect): if 'area' in rect: return rect['area'] rect['area'] = rect['length'] * rect['width'] return rect['area'] print area(rectangle) rectangle['length'] = 15 print area(rectangle) # compare expected vs. actual output! # imagine the same thing with object attributes rather than dictionary keys.

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  • SQLite3's dynamic typing

    - by Bradford Larsen
    SQLite3 uses dynamic typing rather than static typing, in contrast to other flavors of SQL. The SQLite website reads: Most SQL database engines (every SQL database engine other than SQLite, as far as we know) uses static, rigid typing. With static typing, the datatype of a value is determined by its container - the particular column in which the value is stored. SQLite uses a more general dynamic type system. In SQLite, the datatype of a value is associated with the value itself, not with its container. It seems to me that this is exactly what you don't want, as it lets you store, for example, strings in integer columns. The page continues: ...the dynamic typing in SQLite allows it to do things which are not possible in traditional rigidly typed databases. I have two questions: The use case question: What are some examples where sqlite3's dynamic typing is, in fact, beneficial? The historical/design question: What was the motivation for implementing sqlite with dynamic typing?

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  • Does fast typing influence fast programming?

    - by Lukasz Lew
    Many young programmers think that their bottleneck is typing speed. After some experience one realizes that it is not the case, you have to think much more than type. At some point my room-mate forced me to turn of the light (he sleeps during the night). I had to learn to touch type and I experienced an actual improvement in programming skill. The most surprising was that the improvement not due to sheer typing speed, but to a change in mindset. I'm less afraid now to try new things and refactor them later if they work well. It's like having a new tool in the bag. Have anyone of you had similar experience? Now I trained a touch typing a little with KTouch. I find auto-generate lessons the best. I can use this program to create new lessons out of text files but it's only verbatim training, not auto-generated based on a language model. Do you know any touch typing program that allows creation of custom, but randomized lessons?

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  • Optional structural typing possibilty in C++ or anyother language?

    - by ambhai
    In C++ how to tell compiler that Ogre::Vector3 IS_SAME_AS SomeOtherLIB::Vector3 ? I feel that.. in languages like c++ which are not structural typed but there are cases when it makes sense. Normally as game developer when working with 4+ libraries that provide sort or their own Vector3 implementation. The code is littered with ToOgre, ToThis, ToThat conversion function. Thats a lot of Float3 copying around which should not happen on first place. Is in C++ or any other languages where we dont have to convert (copying) from one type to another which is essentially the samething. But any solution in C++ as most of the good gamedevs libs are for c/c++.

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  • Typing lag in WinXP

    - by Ssvarc
    I'm working on a Dell Vostro 1000 laptop that has a mysterious lag in typing. You enter keystrokes and it takes a while to show up on the screen. WinXP Pro was freshly installed and the behavior is still here. Here is the weird part... I've tested the computer with the full Dell diagnostic suite, Prime95 (using UBCD4Win), and Memtest86. Everything checks out as fine. If I run a LiveCD such as UBCD4Win or Ubuntu (9.04?) then there is no typing issue. This is causing me lots of aggravation. Thoughts?

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  • Passthrough Objects – Duck Typing++

    - by EltonStoneman
    [Source: http://geekswithblogs.net/EltonStoneman] Can't see a genuine use for this, but I got the idea in my head and wanted to work it through. It's an extension to the idea of duck typing, for scenarios where types have similar behaviour, but implemented in differently-named members. So you may have a set of objects you want to treat as an interface, which don't implement the interface explicitly, and don't have the same member names so they can't be duck-typed into implicitly implementing the interface. In a fictitious example, I want to call Get on whichever ICache implementation is current, and have the call passed through to the relevant method – whether it's called Read, Retrieve or whatever: A sample implementation is up on github here: PassthroughSample. This uses Castle's DynamicProxy behind the scenes in the same way as my duck typing sample, but allows you to configure the passthrough to specify how the inner (implementation) and outer (interface) members are mapped:       var setup = new Passthrough();     var cache = setup.Create("PassthroughSample.Tests.Stubs.AspNetCache, PassthroughSample.Tests")                             .WithPassthrough("Name", "CacheName")                             .WithPassthrough("Get", "Retrieve")                             .WithPassthrough("Set", "Insert")                             .As<ICache>(); - or using some ugly Lambdas to avoid the strings :     Expression<Func<ICache, string, object>> get = (o, s) => o.Get(s);     Expression<Func<Memcached, string, object>> read = (i, s) => i.Read(s);     Expression<Action<ICache, string, object>> set = (o, s, obj) => o.Set(s, obj);     Expression<Action<Memcached, string, object>> insert = (i, s, obj) => i.Put(s, obj);       ICache cache = new Passthrough<ICache, Memcached>()                     .Create()                     .WithPassthrough(o => o.Name, i => i.InstanceName)                     .WithPassthrough(get, read)                     .WithPassthrough(set, insert)                     .As();   - or even in config:   ICache cache = Passthrough.GetConfigured<ICache>(); ...  <passthrough>     <types>       <typename="PassthroughSample.Tests.Stubs.ICache, PassthroughSample.Tests"             passesThroughTo="PassthroughSample.Tests.Stubs.AppFabricCache, PassthroughSample.Tests">         <members>           <membername="Name"passesThroughTo="RegionName"/>           <membername="Get"passesThroughTo="Out"/>           <membername="Set"passesThroughTo="In"/>         </members>       </type>   Possibly useful for injecting stubs for dependencies in tests, when your application code isn't using an IoC container. Possibly it also has an alternative implementation using .NET 4.0 dynamic objects, rather than the dynamic proxy.

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  • Are there any empirical studies on the effect of different languages on software quality?

    - by jgre
    The proponents of functional programming languages assert that functional programming makes it easier to reason about code. Those in favor of statically typed languages say that their compilers catch enough errors to make up for the additional complexity of type systems. But everything I read on these topics is based on rational argument, not on empirical data. Are there any empirical studies on what effects the different categories of programming languages have on defect rates or other quality metrics? (The answers to this question seem to indicate that there are no such studies, at least not for the dynamic vs. static debate)

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