Inline type value with () in C ++

Question

What does this mean when the built-in type has brackets with it.

eg. int () or float ()

Is it the default constructor or has a different meaning for the built-in types?

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To add more context:

In my school textbook for C ++, I am in the chapter on templates. The template used for the demonstration is a Table template (2D array). One of the functions of the Table is a resizing method for resizing the table and is also used in some constructors used for the Table . This constructor and resizing method:

template <typename T> Table<T>::Table<T>(int m, int n) { mDataMatrix = 0; mNumRows = 0; mNumCols = 0; resize(m, n, T()); } 

and

 template <typename T> void Table<T>::resize(int m, int n, const T& value) { // Destroy the previous data. destroy(); // Save dimensions. mNumRows = m; mNumCols = n; // Allocate a row (array) of pointers. mDataMatrix = new T*[mNumRows]; // Now, loop through each pointer in this row array. for(int i = 0; i < mNumRows; ++i) { // And allocate a column (array) to build the table. mDataMatrix[i] = new T[mNumCols]; // Now loop through each element in this row[i] // and copy 'value' into it. for(int j = 0; j < mNumCols; ++j) mDataMatrix[i][j] = value; } } 

In the constructor definition, resizing the third argument is T () (and I assume that T becomes who the specified type for the template was specified).

In the definition for resize, T () is used for the value argument to assign a default value to the elements in the table.

Of some earlier answers, this is zero initialization. I assume this means that the value is 0 for each element of the table (or some equivalent 0 if the type is a string, I think). Is it correct?

Answer 1

This is initialization of values .

eg. auto x = int(); means int x = 0

In the above example, T() will create an object of type T and pass it as a parameter.

You can also write:

 resize(m, n, T{}); 

Answer 2

In other words, your code does something different than when you declare only int or float . It initializes numbers to zero.

For example, these three lines are equivalent:

 int a = int(); int a = int{}; int a{}; 

All three of these are initialized to zero.