From fbfd23e9a1e2d4dd874a75a968c1cae213ebb564 Mon Sep 17 00:00:00 2001
From: Rishabh <53911515+Rishabh672003@users.noreply.github.com>
Date: Mon, 11 Dec 2023 23:10:41 +0530
Subject: [PATCH] add type-casting for cpp

---
 CPP/32.type-casting.md | 78 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 CPP/32.type-casting.md

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+# Type Casting
+
+Type casting in C++ is a way of converting an object of one data type into another. It allows you to change the data
+type of a variable or expression. There are two types of type conversion: implicit and explicit.
+
+**Implicit Type Conversion**: Also known as 'automatic type conversion', it is done by the compiler on its own, without
+any external trigger from the user. It generally takes place when in an expression more than one data type is present.
+In such conditions, type conversion (type promotion) takes place to avoid loss of data. All the data types of the
+variables are upgraded to the data type of the variable with the largest data type. However, it is possible for implicit
+conversions to lose information, signs can be lost (when signed is implicitly converted to unsigned), and overflow can
+occur (when long long is implicitly converted to float)
+
+**Explicit Type Conversion**: This process is also called type casting and it is user-defined. Here the user can
+typecast the result to make it of a particular data type. In C++, it can be done by two ways:
+
+1. **Converting by assignment**: This is done by explicitly defining the required type in front of the expression in
+   parenthesis. This can be also considered as forceful casting.
+
+```cpp
+double x = 1.2;
+// Explicit conversion from double to int
+int sum = (int)x + 1;
+```
+
+2. **Conversion using Cast operator**: A Cast operator is an unary operator which forces one data type to be converted
+   into another data type.
+
+```cpp
+float f = 3.5;
+// using cast operator
+int b = static_cast<int>(f);
+```
+
+C++ supports four types of casting:
+
+1. **static_cast**: This is the most commonly used type of casting in C++. It can be used for conversions between
+   related types (like from a base class pointer to a derived class pointer), among other things. It can also be used
+   for conversions between unrelated types, such as from an int to a float. However, it does not perform any runtime
+   checks, so it's up to the programmer to ensure the cast is safe.
+
+```cpp
+double x = 10.3;
+int y;
+y = static_cast<int>(x); // y is now 10
+```
+
+2. **const_cast**: This is used to add or remove the const or volatile qualifier from a variable. It can be used to
+   modify a const object, which is undefined behavior in C++.
+
+```cpp
+const char* c = "sample text";
+char* nonConst = const_cast<char*>(c); // nonConst now points to "sample text"
+```
+
+3. **dynamic_cast**: This is used for downcasting in the context of inheritance. It can be used to safely downcast a
+   pointer or reference to a base class to a derived class. If the object is not of the target type, dynamic_cast
+   returns null for pointers or throws a std::bad_cast exception for references.
+
+```cpp
+class Base {};
+class Derived : public Base {};
+Base* a = new Base;
+Derived* b = dynamic_cast<Derived*>(a); // b is null
+```
+
+4. **reinterpret_cast**: This is the most powerful type of cast. It can convert any pointer type to any other pointer
+   type, regardless of the classes they point to. It can also be used to convert any pointer type to an integer type and
+   vice versa. It's the least safe type of cast and should be used sparingly.
+
+```cpp
+int* pi = new int(3);
+char* pc =
+    reinterpret_cast<char*>(pi); // pc now points to the same memory as pi
+```
+
+It's important to note that while these casts can be very useful, they should be used judiciously. Incorrect use of type
+casting can lead to bugs that are hard to detect and fix. Always prefer safer casts (like static_cast and dynamic_cast)
+over more dangerous ones (like reinterpret_cast), and only use const_cast when necessary to modify a const object.