Pointer function arguments

08-pointers/pointer-function-arguments.c

@@ -1,15 +1,91 @@
 /* 
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- Tutorial: brief description of tutorial content
+ Tutorial: This tutorial explains the concept of function pointers as argument in C.
+
+ We cannot pass a function as an argument to another function, but we can pass the
+ reference of a function as a parameter by using a function pointer. This process is
+ known as call by reference. 
+
+ C programming allows you to create a pointer pointing to the function, which can be
+ further passed as an argument to the function. We can create a function pointer as follows:
+
+(return_type) (*point_name) (parameter1, parameter2, ...);
+
+In the above syntax:
+  -> return_type: the variable type which is returned by the function
+  -> *pointer_name: the function pointer
+  -> parameter1, parameter2, ... : the list of parameters passed to the function
+
+e.g:
+  float (*add)();     this is a valid declaration for the function pointer
+  float *add();       this is an illegal declaration for the funciton pointer
+
+A function pointer can also point to another function, or we can say that it holds
+the address of another function.
+
+We can then pass the function pointer as a parameter:
+
+ 1. We need a function F1 that takes as a parameter a function pointer of type TYPE1.
+ 2. We need a function of type TYPE1, meaning it has the same return type and same type
+    of arguments in order. Let's call this function Function2
+ 3. We declare a pointer function of type TYPE1. Let's call it FunctionPointer.
+ 4. We assign Function2 to FunctionPointer:   FunctionPointer = Function2
+ 5. We then call function F1 with FunctionPointer as a parameter. 
+
+We shall see an illustration of this in the example below.
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 */
 
 // Code here explaining concept with comments to guide
+#include <stdio.h>
+
+// function declaration
+int add(int a, int b)
+{
+        return a + b;
+}
+
+void f(int x)
+{
+  printf("%d\n", x);
+}
+
+// another function declaration
+void display(void (*p)(int))
+{
+    for (int i=1; i <= 5; i++)
+    {
+        p(i);
+    }
+}
+
 int main()
 {
+    /* declaration of a pointer to a function that returns a integer and takes as arguments
+    2 integers */
+    int (*a)(int, int);
+    // assigning address of add() to the function pointer "a"
+    a = add;      // Now, 'a' is a pointer pointing to the add()
+
+    // We can call the add() function by using the pointer, i.e., 'a'.
+    printf("%d", a(2, 3));  // prints add(2,3) = 5.0
+
+
+    // How we can pass a function pointer as parameter
+
+    void (*p)(int);     // void function pointer declaration
+    p = f;
+    printf("The values are :");
+    display(p);  // prints 1, 2, 3, 4, 5 each in a new line
+    return 0;
 }
+
 /*
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- Challenge: list challenges to be completed here. minimum of one challenge per tutorial
+ Challenge: 
+ 1. Write a function that prints "I love pointers!"
+ 2. Declare a corresponding function pointer and assign the previous function to it.
+ 3. Write a second function with the correspoing function pointer type as parameter.
+ 4. Call the second function with the first function as a parameter.
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 */