Can Auto Be Used as a Function Argument in C ?

Can Auto Be Used As an Argument in C ?

In C , passing auto as an argument to another function has been a subject of debate. Previously, it was not possible due to ambiguity in type inference. However, C 20 introduced significant changes that allow this functionality.

C 20: Unconstrained Auto Parameter

C 20 allows auto to be used as a function parameter type, known as an "unconstrained auto parameter." This feature provides maximum flexibility by allowing any type to be passed without constraints.

int function(auto data)
{
    // Do something, no constraints on data
}

This syntax is equivalent to defining an abbreviated function template, which can accept any type.

C 20: Constrained Auto Parameter

In addition to unconstrained auto parameters, C 20 also supports constrained auto parameters using concepts. Concepts are constraints that specify requirements for types.

void function(const Sortable auto& data)
{
    // Do something that requires data to be Sortable
    // Assuming there is a concept named Sortable
}

In this example, the Sortable concept constrains the type of data to types that implement the Sortable interface.

Abbreviated Function Templates

Unconstrained auto parameters can be used to create abbreviated function templates. Abbreviated function templates are template functions that deduce their template arguments from the function arguments. This allows for more concise and flexible function declarations.

template<typename T>
void print(T data)
{
    std::cout << data << std::endl;
}

int main()
{
    auto data = 42;
    print(data); // Assumed to print 42
}

In this example, the print function is an abbreviated function template that deduces the type of data based on the provided argument.

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