Converting a variable from one type to another

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29
votes
7answers
41k views

Type casting variables in PHP, what is the practical reason for doing this?

PHP, as most of us know, has weak typing. For those who don't, PHP.net says: PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined ...
0
votes
0answers
56 views

How do the conversions between signed, unsigned and float types work? [migrated]

The compiler I use is g++ (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4. I compile my programs with the following command: g++ -std=c++11 -pedantic -Wall program.cpp The program no. 1.: #include ...
7
votes
6answers
4k views

How to avoid downcasting?

My question is about a special case of the super class Animal. My Animal can moveForward() and eat(). Seal extends Animal. Dog extends Animal. And there's a special creature that also extends ...
0
votes
0answers
81 views

Type checking in factory, bad practice?

I'm working on an existing code base and am trying to reduce a lot of duplication and gain some polymorphic behavior. Right now I have a type of domain object with an abstract base class and two (at ...
3
votes
1answer
3k views

Java default Integer value is int

My code looks like this import java.util.Scanner; public class StudentGrades { public static void main(String[] argv) { Scanner keyboard = new Scanner(System.in); byte q1 = ...
3
votes
3answers
91 views

How to design access to different type objects in protocol response

I have written a communication library for an industrial device protocol. The response frame contains a byte array as payload data. The payload data consists of several "objects“ of different types, ...
5
votes
4answers
6k views

OOD: Java inheritance and access to child methods via casting

I have several classes Parent and Child1 ... Child9 implemented in Java. Parent is an abstract class, containing all the common variables of the child classes (a lot, which is the main reason why I ...
2
votes
1answer
220 views

What is the motivation for casting a pointer into a integer?

I'm doing some changes in the Linux kernel code and have noticed a pointer being cast into integer. Check out buf below (full code): snd_pcm_sframes_t snd_pcm_lib_read(struct snd_pcm_substream ...
6
votes
2answers
114 views

Is it possible to avoid abstraction inversion in this scenario?

I'm designing a library built on web scraping that tries to provide an API to a popular news site. I am representing each of its articles as a collection of 'elements' (IElement), such as images, ...
2
votes
1answer
84 views

Storing values in SQL whose types are determined in runtime

I have come across a need of storing runtime determined values in a SQL database. For example, there is a GUI where a user can add new editable fields. So the user adds a field Name, chooses the ...
33
votes
10answers
4k views

Is it okay to have objects that cast themselves, even if it pollutes the API of their subclasses?

I have a base class, Base. It has two subclasses, Sub1 and Sub2. Each subclass has some additional methods. For example, Sub1 has Sandwich makeASandwich(Ingredients... ingredients), and Sub2 has ...
22
votes
5answers
4k views

Is my usage of explicit casting operator reasonable or a bad hack?

I have a big object: class BigObject{ public int Id {get;set;} public string FieldA {get;set;} // ... public string FieldZ {get;set;} } and a specialized, DTO-like object: class ...
2
votes
2answers
302 views

When it makes sense to implement C# explicit operator?

Follow-up of Is my usage of explicit casting operator reasonable or a bad hack? One of the users commenting on that question said that it's really bad if the casting operator creates a new object ...
8
votes
3answers
4k views

Is there a difference between casting and converting types in imperative programming languages?

The question came up in a discussion at StackOverflow. Is there a clean distinction between the two concepts cast and convert (concerning the type of an object), or are these two words describing ...
3
votes
3answers
349 views

“One of some”-type

Say that you have some different classes that does not really have any functionality in common, but somewhere in your program, you need one of them (which one is not necessarily important) because ...
11
votes
8answers
11k views

c style casts or c++ style casts

So, what do you use? int anInt = (int)aFloat; or int anInt = static_cast<int>(aFloat); // and its brethren And, more importantly, why?
1
vote
1answer
347 views

Constructor vs casting operator

I'm programming a library (so I have complete access to all the mentioned classes). Two classes (A and B) are essentially the same and differ only by their implementation, so they can be easily ...
6
votes
6answers
1k views

Would a “downcast if block” be a reasonable language feature?

Consider the following "if cast": class A { public void f1() { ... } } class B : A { public void f2() { ... } } A a = foo(); // might return A or B if ( a is B ) { // Inside block, ...
0
votes
2answers
261 views

Optimization ended up in casting an object at each method call

I've been doing some optimization for the following piece of code : public void DrawLine(int x1, int y1, int x2, int y2, int color) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color); } After ...
1
vote
1answer
130 views

Ignoring the generic part of a type while an object is being passed

I have a message class that holds the name of a destination, and a generic variable acting as the message payload public class Message<T> { public string Destination public T Payload ...
2
votes
2answers
1k views

Having an inherited function return the derived type instead of the base type

I am writing two classes in C#: A Matrix class that represents a general Matrix with n-by-m dimensions A SquareMatrix class that inherits from Matrix and has the constraint of being n-by-n The ...
1
vote
3answers
93 views

Property-level value transformation for indirect object casting

Does any programming language exist to support the explicit, property-level object copy? For example, assume this code: public class Student { public string Name { get; set; } public ...
1
vote
3answers
2k views

Make Return Type an Interface - Problem with Initialization

I would like to make the return type of my method an interface rather than a class for similar reasons stated in c# List or IList, however I am having trouble figuring out how to initialize the ...
1
vote
2answers
3k views

A vector of pointers to different derived classes of the same base class

I am writing a game in C++ which has different enemy types. I have defined a base Enemy class and I also have derived classes enemy1, enemy2 etc. Now for updating these enemies in each iteration of ...
1
vote
2answers
4k views

Why doesn't Ruby have implicit conversion of Fixnum into String?

Ruby normally makes things easy. However, it doesn't allow implicitely converting a number to a string: 2.0.0p247 :010 > "a"+1 TypeError: no implicit conversion of Fixnum into String Why is this ...
2
votes
1answer
76 views

Handling Types for Real and Complex Matrices in a BLAS Wrapper

I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write ...
0
votes
2answers
4k views

Question about casting a class in Java with generics

In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ...
-1
votes
3answers
3k views

Is converting/casting a boolean to int a good idea? [closed]

Note: Even though this contains Python, it's not specifically about Python. It's more generally about expecting a certain behaviour from a language which is not necessarily the same across ...
1
vote
1answer
59 views

Removing dependencies on subclass-specific behavior

I have a Message class which can contain multiple types of payloads (or sometimes no payload), each derived from a common Payload class. However, this becomes problematic because the Message class ...
5
votes
2answers
347 views

Is there a name for the number of values a variable can take? [closed]

For example, a bit or a boolean can be either 0 or 1 so the number 2 is associated with it. Similarly, for a byte which is 8 bits, the maximum number of different assignments would be 2^8. Is there a ...
1
vote
1answer
598 views

When is type coercion a good idea?

When do you want (on purpose) to coerce type in JavaScript? I mean, beyond comparing strings and numbers, when does it benefit something you're building? Examples of type coercion: "The answer is " ...
16
votes
4answers
7k views

What is casting supposed to mean?

When coding in low level languages like C I find that casting sometimes means 'reinterpret these bytes as if it had always been of this other type' and at other times as 'convert this value ...
1
vote
1answer
231 views

Loose typing not applied to objects

I have very little experience working with classes and object. I work in a loosely typed language, PHP. I was working with a SimpleXML object and ran into a problem where I was trying to do math with ...
2
votes
2answers
3k views

Type parameterized methods to avoid casting

In a library I am developing I have a factory method that looks a bit like: public <T> T instantiate(Type targetType) { return ...; } I am using a type parameterized method to avoid that ...
0
votes
2answers
190 views

Boolean-Integer Typecasting to Replace Conditional [closed]

When choosing a value based off of 2 boolean values in this format var foo:int; if (X){ foo = 50; } else if (Y){ foo = -50; } else { foo = 0; } I discovered that I can condense this ...
7
votes
2answers
653 views

implement cons function in Java - type safety question

I am working on a small functional library written in Java, which mimics the a functional style of programming. I am stuck with a undesirable type cast in one of my method definitions and would love ...
2
votes
2answers
2k views

C++ Typecasting VS performance

Let's say we're designing a video game. We have some sprites on the map and we want to call some method of the particular sprite at some particular position. We are using one broadly-known C++ ...
4
votes
2answers
365 views

Alternatives to type casting in your domain

In my Domain I have an entity Activity which has a list of ITasks. Each implementation of this task has it's own properties beside the implementation of ITask itself. Now each operation of the ...