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Pointer to Function C and C++

Hi this is my first technical post , really i find this topic very interesting and i like it .
actually I worked now on good project which utilize my Genetic algorithms , neural networks and parallel computing knowledge . when searching i hit in this topic .

pointers to function :
who should read this article are computer science students and programing Students
introduction :
 you can write good code without knowing any thing about pointers , but if you used pointers you will write all your codes with pointers , it is best invention after electricity , it will attract you , and you will feel the infinite happiness  .

what is pointer ?
you know int , float , double you can think on this data type as box which contain some value . but pointers is different it stores the reference of this value -memory address - then you can access the value in this pointer by dereference it .

declare pointer int *ptr;
dereference pointer *ptr ; but take care you have to assign value to the pointer before dereference it to avoid memory explosion .

pointers are amazing in passing arrays to functions .
are amazing two to create dynamic arrays , it can be deleted and free its memory .

about today topic :
Arrays can used to pass function as an argument for another function .
problem statement :
in math you can apply this equation using the two functions f &g  f(g(x))  or more complex than this one .
the problem appear if we need to do some operation  on the same data items and test results , e.g select the best function it is famous on neural networks , classifier and genetic programing .

for example :
write a C++ or C function which take a function as argument and 2 data items x and y . the argument function either addition or subtraction .

solution :

1-#include
2-using namespace std;

3-int addition (int a, int b)
4-{ return (a+b); }

5-int subtraction (int a, int b)
6-{ return (a-b); }

7-int operation (int x, int y, int (*functocall)(int,int))
8-{
9- int g;
10-  g = (*functocall)(x,y);
11-  return (g);
12-}

13-int main ()
14-{
15-  int m,n;
16-  int (*minus)(int,int) = subtraction;

17-  m = operation (7, 5, addition);
18-  n = operation (20, m, minus);
19-  cout <
20-  return 0;
21- }

in the line no.7 the third parameter for the function operation
int (*functocall)(int,int)

int -> is the return type of the function  .

*functocall->pointer to function .

(int,int)-> the arguments of the function both type int .
in the line no.17 and line no. 18 we call the function and put the name of the two functions addition and minus respectively

by the end of this article i hope you learn new thing .

yours,
Ahmed Ghazey


reference : http://www.cplusplus.com/doc/tutorial/pointers/

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