C++ Type conversion

In this tutorial, we will learn C through examples. ++Basic knowledge of type conversion.

C ++Allow us to convert data of one type to another type. This is called type conversion.

C ++There are two types of type conversions.

1. Implicit conversion

2. Explicit conversion (also known as type casting)

Related conversions: convert C ++String converted to int 　C ++ String converted to float / double

Implicit type conversion

The type conversion done automatically by the compiler is called implicit type conversion. This type of conversion is also known asAutomatic conversion.

Let's look at two examples of implicit type conversion.

Example1：From int to double

//　How implicit type conversion works
#include <iostream>
using namespace std;
int main() {
　　　//　Assign an int value to num_int
　　　int num_int　9;
　　　//　Declare a double variable
　　　double num_double
　
　　　//　Implicit conversion
　　　//　Assign an int value to a double variable
　　　num_double = num_int;
　　　cout　<<　"num_int　=　"　<<　num_int　<<　endl;
　　　cout << "num_double = " << num_double << endl;
　　　return 0;
}

Output result

num_int　=　9
num_double =　9

In the program, we have assigned int data to a double variable.

num_double = num_int;

Here, before assigning an int value to the num_double variable, it will be automatically converted to double by the compiler. This is an example of implicit type conversion.

Example2：Automatically from double to int

//How implicit type conversion works
#include <iostream>
using namespace std;
int main() {
　　　int　num_int;
　　　double num_double　9.99;
　　　//　Implicit conversion
　　　//　Assign a double value to an int variable
　　　num_int　=　num_double;
　　　cout　<<　"num_int　=　"　<<　num_int　<<　endl;
　　　cout << "num_double = " << num_double << endl;
　　　return 0;
}

Output result

num_int　=　9
num_double =　9.99

In the program, we have assigned double data to an int variable.

num_double = num_int;

Here, before assigning the double value to the num_int variable, the compiler will automatically convert it to int. This is also an example of implicit type conversion.

Note:Since int cannot have a fractional part, the decimal part was truncated in the above example.

Data loss during conversion (narrowing conversion)

From the above examples, it can be seen that converting from one data type to another can easily lead to data loss. This happens when data of a larger type is converted to a smaller type.

C ++Explicit conversion

When the user manually changes the data from one type to another, this is calledExplicit conversion. This type of conversion is also known asExplicit type conversion.

We can use three main methods in C ++Explicit conversion is used in the C type. They are:

1. C type type cast (also known as cast symbol)

2. Function notation (also known as old-style C++style type conversion)

3. Type Conversion Operators

C style conversion

As the name implies, this type of conversion isC programming language'sAlso known asExplicit conversion notation.

The syntax of this style is:

(data_type)expression;

For example,

//　Initialization of int variable
int num_int　26;
//　Declaration of double variable
double num_double
//　Conversion from int to double
num_double = (double)num_int;

Function style conversion

We can also use functions with similar symbols to convert data from one type to another.

The syntax of this type is:

data_type(expression);

For example,

//　Initialization of int variable
int num_int　26;
//　Declaration of double variable
double num_double
//　Conversion from int to double
num_double = double(num_int);

Example3: Type conversion

#include <iostream>
using namespace std;
int main() {
　　　　//　Initialization of double variable
　　　　double num_double　3.56;
　　　　cout << "num_double = " << num_double << endl;
　　　　//　C style conversion from double to int
　　　　int num_int1　= (int)num_double;
　　　　cout << "num_int1　　　= " << num_int1　<< endl;
　　　　//　Function style conversion from double to int
　　　　int num_int2　= int(num_double);
　　　　cout << "num_int2　　　= " << num_int2　<< endl;
　　　　return 0;
}

Output result

num_double =　3.56
num_int1　　　=　3
num_int2　　　=　3

We useC-style type conversionsandFunction-style casts are used for type conversion,and display the result. Since they perform the same task, they both give us the same output.

Type Conversion Operators

In addition to these two type conversions, C ++There are also four operators for type conversion. They are calledType Conversion OperatorsThey are:

• static_cast

• dynamic_cast

• const_cast

• reinterpret_cast

We will learn these conversions in future tutorials.