Question

Map, Filter, and Reduce are three functions commonly used in functional programming. For this assignment you will be implementing all three, along with three minor functions that can be passed to them.

Map

The map function takes as arguments a function pointer and a integer vector pointer. It applies the function to every element in the vector, storing the results in-order in a new vector. It then returns a pointer to a new vector.

You should pass your square function into map to test it.

Sample Input { 1, 3, 5, 7, 9 }

Expected Output { 1, 9, 25, 49, 81 }

Filter

The filter function takes as arguments a function pointer and a integer vector pointer. It tests every element in the vector against the function, storing in a new vector those elements for which the function returns true. It then returns a pointer to the new vector.

You should pass your isEven function into filter to test it.

Sample Input { 1, 2, 3, 4, 5 }

Expected Output { 2, 4 }

Reduce

The reduce function takes as arguments a function pointer and a integer vector pointer. The reduce function reduces a vector down to a single value by passing a running total and next vector element to the function, then storing the results as the new total. It does this for every element of the vector.

reduce (fxn, array) acc = array[0] for i in array[1 ... n]: acc = fxn(acc,i) return acc

Sample Input { 1, 2, 3, 4 }

Expected Output 24

You should pass your product function into reduce to test it.

Minor Functions

You will also need to implement these three additional functions to be used with map, filter, and reduce respectively.

square Takes an integer and returns its square

isEven Takes an integer and returns true if even, otherwise false

product Takes two integers and returns their product

Function declarations for all six functions are at the top of the main file. Your assignment is to create the bodies for all six functions

I have created unit tests for all six functions. The unit tests function independently of the main method and system output, so you are free to use the main method and cout << for your own development, testing, and debugging.

NB: You should never modify the vector passed into the map, filter, and reduce methods. Treat them as read only.

Code Given:

#include <iostream>

#include <vector>

using namespace std;

vector<int> * map ( int (*fxn) (int), vector<int> * vec );

vector<int> * filter ( bool (*fxn) (int), vector<int> * vec );

int reduce ( int (*fxn) (int, int), vector<int> * vec );

int square (int); // For use with map

bool isEven (int); // For use with filter

int product (int,int); // For use with reduce

bool testPassed();

int main ( ) {

/* Use the main method for your own testing, debugging, etc */

}

Answer 1

#include <iostream>
#include <stdlib.h>
#include <vector>
using namespace std;

vector<int> v;
bool isEven (int);  

int square (int d){
return d*d;
}
bool isEven (int e){

return (e%2)==0;
} // For use with filter
int product (int a,int b){
return a*b;

}
vector<int> * map ( int (*fxn) (int), vector<int> * vec ){
v.clear();
v = *vec;
for(int i = 0 ;i<v.size();++i){
int d = fxn(v[i]);
(v[i]) = d;
}
  
return &v;
  
}

vector<int> * filter ( bool (*fxn) (int), vector<int> * vec ){
v.clear();
vector<int> v1 = *vec;
for(int i = 0 ;i<v1.size();++i){
bool d = fxn(v1[i]);
if(d)
v.push_back(v1[i]);
}
  
return &v;
  
}
int reduce ( int (*fxn) (int, int), vector<int> * vec ){
vector<int> v1 = *vec;
int d = 1;
for(int i = 0 ;i<v1.size();++i){
d = fxn(d , v1[i]);
}
  
return d;
}

// For use with map

// For use with reduce

bool testPassed();


int main ( ) {

/* Use the main method for your own testing, debugging, etc */

vector<int>vec;
vec.push_back(1);
vec.push_back(3);
vec.push_back(5);
vec.push_back(7);
vec.push_back(9);
int (*fun_ptr)(int) = &square;


vector<int> * m = map(fun_ptr, &vec);
vector<int> v = *m;
cout<<"After calling map method: "<<endl;
for(int i = 0 ;i<v.size();++i){
cout<< v[i] <<" ";
}
cout<<endl;
bool (*fun)(int) = &isEven;
  
vector<int>vec1;
vec1.push_back(1);
vec1.push_back(2);
vec1.push_back(3);
vec1.push_back(4);
vec1.push_back(5);
vector<int> * p = filter(fun, &vec1);
vector<int> p1 = *p;
cout<<"After calling filter method: "<<endl;
for(int i = 0 ;i<p1.size();++i){
cout<< p1[i] <<" ";
}
  
cout<<endl;
vector<int>prod;
prod.push_back(1);
prod.push_back(2);
prod.push_back(3);
prod.push_back(4);
int (*fun1)(int, int) = &product;
int val = reduce(fun1, &prod);
cout<<"Product is: " <<val<<endl;
  

}

=======================================================================
See Output

After calling map method: 1 9 25 49 81 After calling filter method: 3 vector<int>map int (*fxn) (int), vector<int» * vec )1 v.clearO; = *vec ; for(int i-0 ;i<v.size);++i) Product is: 24 int d fxn(v[i]); return &v; 6 vector<int> * filter ( bool (*fxn) (int), vector<int> *vec v.clearO; vector<int> for(int v1 0 bool d- fxn(v1[i]); *vec ; = 1 ;i<v1 . size();++i){ = if(d) v.push_back(v1[i]); return &v; 8int reduce ( int (*fxn) (int, int), vector<int *vec vector<int> int d=1; v1 "Vec;


Thanks, let me know if there is any concern. Comment and I will surely respond for any doubts/clarification. Please rate if you think its helpful