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Questions tagged [casting]

Casting is a process where an object type is explicitly converted into another type if the conversion is allowed. This process might lead to a change in value.

Some algorithms have significant performance differences for different data-types, for example, calculating the N-dimensional median is much is much faster for integers than float type data. Therefore, the use of casting can be important for code performance.

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Any difference between type assertions and the newer `as` operator in TypeScript?

Is there any difference between what the TypeScript spec calls a type assertion: var circle = createShape("circle"); And the newer as operator: var circle = createShape("circle") as Circle; Both of which are typically used for…
mk.
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How to check that a string is an int, but not a double, etc.?

PHP has an intval() function that will convert a string to an integer. However I want to check that the string is an integer beforehand, so that I can give a helpful error message to the user if it's wrong. PHP has is_int(), but that returns false…
Amandasaurus
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How to cast/convert pointer to reference in C++

How can I pass a pointer (Object *ob) to a function which prototype is void foo(Object &) ?
Dewsworld
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In Objective-C, what is the equivalent of Java's "instanceof" keyword?

I would like to check whether an object (e.g. someObject) is assignable (cast-able) to a variable of another type (e.g. SpecifiedType). In Java, I can write: someObject instanceof SpecifiedType A related question is finding whether the runtime type…
Dimitris
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convert double to int

What is the best way to convert a double to an int? Should a cast be used?
user496949
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Value of type 'T' cannot be converted to

This is likely a a novice question, but google surprisingly did not provide an answer. I have this rather artificial method T HowToCast(T t) { if (typeof(T) == typeof(string)) { T newT1 = "some text"; T newT2 = (string)t; …
Alex
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Android: How can I Convert String to Date?

I store current time in database each time application starts by user. Calendar c = Calendar.getInstance(); String str = c.getTime().toString(); Log.i("Current time", str); In database side, I store current time as string (as you see in…
Hesam
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Explicit casting from super-class to sub-class

public class Animal { public void eat() {} } public class Dog extends Animal { public void eat() {} public void main(String[] args) { Animal animal = new Animal(); Dog dog = (Dog) animal; } } The assignment Dog dog…
saravanan
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How to insert a character in a string at a certain position?

I'm getting in an int with a 6 digit value. I want to display it as a String with a decimal point (.) at 2 digits from the end of int. I wanted to use a float but was suggested to use String for a better display output (instead of 1234.5 will be…
daverocks
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Kotlin: How to work with List casts: Unchecked Cast: kotlin.collections.List to kotlin.colletions.List

I want to write a function that returns every item in a List that is not the first or the last item (a via point). The function gets a generic List<*> as input. A result should only be returned if the elements of the list are of the type…
Lukas Lechner
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dynamic_cast and static_cast in C++

I am quite confused with the dynamic_cast keyword in C++. struct A { virtual void f() { } }; struct B : public A { }; struct C { }; void f () { A a; B b; A* ap = &b; B* b1 = dynamic_cast (&a); // NULL, because 'a' is not a…
Vijay
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Cast Object to Generic Type for returning

Is there a way to cast an object to return value of a method? I tried this way but it gave a compile time exception in "instanceof" part: public static T convertInstanceOfObject(Object o) { if (o instanceof T) { return (T) o; }…
sedran
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Cast object to interface in TypeScript

I'm trying to make a cast in my code from the body of a request in express (using body-parser middleware) to an interface, but it's not enforcing type safety. This is my interface: export interface IToDoDto { description: string; status:…
Elias Garcia
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Assignment in an if statement

I have a class Animal, and its subclass Dog. I often find myself coding the following lines: if (animal is Dog) { Dog dog = animal as Dog; dog.Name; ... } For the variable Animal animal;. Is there some syntax that allows me to…
michael
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In C, why do some people cast the pointer before freeing it?

I'm working on an old code base and pretty much every invocation of free() uses a cast on its argument. For example, free((float *)velocity); free((float *)acceleration); free((char *)label); where each pointer is of the corresponding (and…
SO Stinks
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