numeric header in C++ STL | Set 2 (adjacent_difference(), inner_product() and iota())

Difficulty Level : Medium
Last Updated : 06 Jul, 2017

adjacent_difference

This functions assigns the difference between the corresponding elements of an array to another array. It returns the adjacent difference of all the set of values lying between [ First, last ).

For Example: If a[] represents an element in provided range [first, last) and b[] represents the result.

b[0] = a[1] 
b[1] = a[1] – a[0] 
b[2] = a[2] – a[1] 
b[3] = a[3] – a[2] 
b[4] = a[4] – a[3] 
... ... ...

Syntax:

adjacent_difference(first, last, b);
adjacent_difference(first, last, b, myfun );
adjacent_difference(first, last, b, multiplies() ) ;

first, last : address of first and last element of range whose elements are to be added
b:index of array where  corresponding partial sum will be stored;
myfun : a user defined function for performing any specific task
multiplies():a pre defined function.

#include <iostream>  
#include <functional> // for multiplies function 
#include <numeric>   //for adjacent_difference 
  
using namespace std; 
  
int myfun (int x, int y)  
{ 
    return x+y; 
} 
  
int main ()  
{ 
    int a[] = { 1, 2, 3, 4, 5, 6} ; 
    int b[6]; 
      
    // using adjacent_difference function 
    adjacent_difference (a, a+6, b); 
    cout << "\nResult using adjacent_difference: "; 
    for (int i=0; i<6; i++)  
        std::cout << b[i] << ' ' ;    
      
    // using adjacent_difference function 
    // user defined function     
    adjacent_difference (a, a+6, b, myfun); 
    cout << "\nResult using accumulate with user-"
             "defined function: "; 
    for (int i=0; i<6; i++)  
        std::cout << b[i] << ' '; 
      
    // using adjacent_difference with pre-defined function 
    adjacent_difference (a, a+6, b, multiplies<int>() ) ; 
      
    cout << "\nResult using accumulate with pre-defined function: " ; 
    for (int i=0; i<6; i++)  
        std::cout << b[i] << ' '; 
      
    return 0; 
} 

Output:

Result using adjacent_difference: 1 1 1 1 1 1 
Result using accumulate with user-defined function: 1 3 5 7 9 11 
Result using accumulate with pre-defined function: 1 2 6 12 20 30

inner_product

This function returns the result of addition of var with the inner products of the pairs formed by the elements of two ranges starting at first1 and first2.

Syntax:

inner_product(first, last, b, var) ;
inner_product(a, a+3, b, var, fun, fun1) ;
inner_product(a , a+3, b, init, minus (), divides () );

first, last : address of first and last element of range whose elements are to be added
b: index of array where  corresponding partial sum will be stored;
fun, fun1: a user defined function for performing any specific task
minus(), divides()  : pre defined function.

#include <iostream>   
#include <functional> // for subtraction, std::divides 
#include <numeric>   // for inner_product 
  
using namespace std; 
  
int fun (int x, int y)  
{ 
    return x-y; 
} 
  
int fun1 (int x, int y)  
{ 
    return x+y; 
} 
  
int main ()  
{ 
    int var = 200; 
    int a[] = { 10, 15, 20} ; 
    int b[] = { 1, 3, 5} ; 
      
    cout << "\nResult using inner_product " ;     
  
    // inner_product with default method 
    cout << inner_product(a, a+3, b, var ) ; 
      
    // inner_product with pre-defined function 
    cout << "\nResult using inner_product with pre-defined function: "; 
    cout << inner_product(a, a+3, b, var, minus<int>(), divides<int>()); 
      
    // inner_product with user defined function 
    cout << "\nResult using inner_product with user-defined function: "; 
    cout << inner_product(a, a+3, b, var, fun, fun1); 
  
    return 0; 
} 

Output:

Result using inner_product 355
Result using inner_product with pre-defined function: 181
Result using inner_product with user-defined function: 146

iota

This function assigns a value to the elements in the range [first,last ) of the array which is incremented at each step by val++ .

Syntax –

iota(first, last,val) ;

first, last : address of first and last element of range whose elements are to be added
val: initial value to store, the expression ++value must be well-formed

#include <iostream>  
#include <iostream>  
#include <numeric>   // std::iota 
using namespace std; 
  
int main ( ) 
{ 
    int a[7]; 
      
    //using iota function to store 100, 101, 102,...     
    iota(a, a+7,100); 
    cout << " a : " ; 
    for (int& x: a)  
        cout << ' ' << x; 
      
    return 0; 
} 

Output :

a: 100 101 102 103 104 105 106

This article is contributed by Abhinav Tiwari . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Attention reader! Don’t stop learning now. Get hold of all the important C++ Foundation and STL concepts with the C++ Foundation and STL courses at a student-friendly price and become industry ready.

My Personal Notes

Related Articles