How Do Callbacks Enhance Flexibility and Customization in C ?

Callbacks in C

A callback is a callable object that is passed as an argument to a function or class, allowing for customization of the behavior based on the specific callback function.

Reasons to use Callbacks:

• Writing generic code that can work with different logic provided by the callback
• Notifying callers of certain events, providing flexibility at runtime
• Enabling dynamic behavior during runtime

Callables in C 11:

• Function pointers (including pointers to member functions)
• std::function objects
• Lambda expressions
• Bind expressions
• Function objects (classes with overloaded function call operator())

Writing Function Pointers:

int (*)(int); // Function pointer type taking one int argument, returning int
int (* foo_p)(int) = &foo; // Initialize pointer to function foo

Call Notation:

int foobar(int x, int (*moo)(int));
foobar(a, &foo); // Call foobar with pointer to foo as callback

std::function Objects:

std::function<int(int)> stdf_foo = &amp;foo;

Call Notation:

int stdf_foobar(int x, std::function<int(int)> moo);
stdf_foobar(a, stdf_foo);

Lambda Expressions:

stdf_foobar(a, [c](int x) -> int { return 7+c*x; });

std::bind Expressions:

int nine_x_and_y (int x, int y) { return 9*x + y; }
stdf_foobar(a, std::bind(nine_x_and_y, _1, 3));

Templated Callbacks:

template<class R, class T>
void stdf_transform_every_int_templ(int * v,
  unsigned const n, std::function<R(T)> fp) {...}

Call Notation:

stdf_transform_every_int_templ<int,int&amp;>(&amp;a[0], 5, &amp;woof);

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