Static type checking means that type checking occurs at compile time. No type information is used at runtime in that case. Dynamic type checking occurs when type information is used at runtime. Furthermore, you can use the typeid operator to find out about the runtime type of objects. For example, you can use it to check whether the shape in the example is a circle or a rectangle.
Here is some further information. Both can be used only when RTTI support is enabled in compiler. If you attempt to cast to pointer to a type that is not a type of actual object, the result of the cast will be NULL. Make sure there is atleast one virtual function in Base class to make dynamicast work.
Note that a and b have a static type that is fixed by it's declaration - it doesn't matter what you put in them, they will keep the same static type. Sometimes you don't know what the dynamic type is - e. Typically, if you're using this sort of code, you want to be able to do delete a ; for that to work A 's destructor has to be virtual. Static type checking is type checking that is done at compile time. From what I have read in many many efforts to research the answer is that COM objects are considered easier to use, and using a wrapper instead allows for greater control.
In some cases using a wrapper can but not always reduce the size of the thunk, as COM objects automatically have a standard size footprint and wrappers are only as big as they need to be. So another part of my answer should include a warning that crossing the thunk boundary more than absolutely necessary is bad practice, accessing the thunk boundary inside a loop is not recommended, and that it is possible to set up a wrapper incorrectly so that it double thunks crosses the boundary twice where only one thunk is called for without the code seeming to be incorrect to a novice like me.
Two notes about the wmv's. First: some footage is reused in both, don't be fooled. At first they seem the same but they do cover different topics. Second, there are some bonus features such as marshalling that are now a part of the CLI that are not covered in the wmv's. This also means that with either case in development environments you will likely have to copy the library to each directory where applications call it.
There are two ways that you can do this. For example:. An important point to note is that this will check if what ptr points at is exactly a DerivedType. If ptr is pointing at an object of a type derived from DerivedType maybe an EvenMoreDerivedType , this code will not work correctly. I personally find this easier to read and less error-prone, but by all means go with what's easiest for you.
Groovy is dynamically-typed and determines its variables' data types based on their values, so this line is not required. The code above should create the variable number with a value of 5 , then change its value to 10 by adding 15 to it and dividing it by 2.
However, number is misspelled at the beginning of the second line. Because Groovy does not require you to declare your variables, it creates a new variable called numbr and assigns it the value number should have. This code will compile just fine, but may produce an error later on when the script tries to do something with number assuming its value is The reason for this is that many useful features or properties are difficult or impossible to verify statically.
For example, suppose that a program defines two types, A and B, where B is a subtype of A. If the program tries to convert a value of type A to type B, which is known as downcasting , then the operation is legal only if the value being converted is actually a value of type B. Therefore, a dynamic check is needed to verify that the operation is safe.
Other language features that dynamic-typing enable include dynamic dispatch , late binding , and reflection. In contrast to static type checking, dynamic type checking may cause a program to fail at runtime due to type errors. In some programming languages, it is possible to anticipate and recover from these failures — either by error handling or poor type safety. In others, type checking errors are considered fatal.
Because type errors are more difficult to determine in dynamic type checking, it is a common practice to supplement development in these languages with unit testing. All in all, dynamic type checking typically results in less optimized code than does static type checking; it also includes the possibility of runtime type errors and forces runtime checks to occur for every execution of the program instead of just at compile-time.
However, it opens up the doors for more powerful language features and makes certain other development practices significantly easier. For example, metaprogramming — especially when using eval functions — is not impossible in statically-typed languages, but it is much, much easier to work with in dynamically-typed languages. A common misconception is to assume that all statically-typed languages are also strongly-typed languages, and that dynamically-typed languages are also weakly-typed languages.
A strongly-typed language is one in which variables are bound to specific data types, and will result in type errors if types to not match up as expected in the expression — regardless of when type checking occurs. A simple way to think of strongly-typed languages is to consider them to have high degrees of type safety.
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