Can You Overload the Comma Operator in C ?

When Overload Overload the Comma Operator in C

The comma operator (,) in C has primarily been known for its primary function of separating expressions. However, it also offers the option of overloading.

Practical Uses

One practical application of overloading the comma operator is in working with multi-dimensional data structures. For instance, consider a scenario where you need to index a map using multiple indices. Instead of resorting to complex indexing mechanisms, you can overload the comma operator to simplify the process.

The following example illustrates this approach:

<code class="cpp">enum Place {new_york, washington, ...};

pair<Place, Place> operator , (Place p1, Place p2)
{
    return make_pair(p1, p2);
}

map< pair<Place, Place>, double> distance;

distance[new_york, washington] = 100;</code>

In this code, the comma operator is overloaded to create a pair of Place values, which is then used as the key for the distance map. The resulting syntax provides an intuitive and concise way to index the map with multiple place names.

Deprecation Notice

It is important to note that using the comma operator without enclosing parentheses in an array subscript was deprecated in C 20 and removed in C 23. This deprecated usage can lead to incorrect behavior, so it is recommended to enclose the expression with parentheses to avoid any issues.

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