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

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.

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