c++ - cannot display the result of each one of my function -

i wrote code computes sum of components of array randomly filled values between 0 , 1. have write 2 functions, 1 iterative, , other 1 recursive. both should same work. 2 functions wrote work fine when call 1 @ time. however, if try call 2 functions in main, can see result of 1 only, cannot see result other one. in addition, recursive function tends called 1 time. have noticed if put getch() comment in recursive_function(). know missing something, cannot figure out. help. here code. using dev-c++.

#include <iostream> #include<conio.h> #include <stdlib.h>  using namespace std;  //headers of thre functions int random_value(int array[], int size); int iterative_function (int array[], int size, int sum); int recursive_function ( int size, int array[], int index, int sum);    int main() {         int size;int array[size]; int sum=0;    int index=0;    cout<<"enter size of array"<<endl;    cin>>size;                //enter size ofthe array...    random_value(array, size);    iterative_function (array, size, sum);     recursive_function ( size, array, index, sum);    getch();    return 0; }  int random_value(int array[], int size) {  cout<<"here value returned rand()"<<endl;    for(int i=0;i<size;i++)    { array[i]=( rand() % (0-2));      cout<<array[i]<<endl;    } }  int iterative_function (int array[], int size, int sum) {    int i,j, number, value; i=0;    cout<<"from iterative function"<<endl;    cout<<"------"<<endl;    for(i=0;i<size;i++)    sum=sum+array[i];    cout<<"sum of array="<<sum<<endl;               getch();    return 0;      //exit function. program terminated succesfully. }  int recursive_function ( int size, int array[], int index, int sum) {   if(size>index)   {       sum=sum+array[index];     index++;     recursive_function( size, array, index, sum);    }   cout<<"from recursive function"<<endl;   cout<<"------"<<endl;   cout<<"new sum= "<< sum<<endl;    getch();   return 0;  } 

#include <iostream> #include<conio.h> 

<conio.h not standard header, i.e. not available compilers, , don't need it.

to see result output of program:

• run command line, or

• in visual studio run via keypress [ctrl f5] (no debugging), or

• set breakpoint on closing brace of main, , run under debugger (in visual studio e.g. via keypress [f5]).

#include <stdlib.h> 

as far can see you’re not using header. however, provide symbolic constants exit_success , exit_failure, intended return statement in main. e.g., can more clear write exit_success there write 0, because many folks misunderstand 0 means in context.

using namespace std; 

this ok short program or within namespace.

however, keep in mind short programs end not-so-short programs.

and using namespace std; can cause name collisions, in particular name std::distance.

//headers of thre functions int random_value(int array[], int size); int iterative_function (int array[], int size, int sum); int recursive_function ( int size, int array[], int index, int sum); 

although partly matter of preference, there no advantage in forward-declaring functions before main, more work, , causes problems when forward declarations don’t quite match definitions – unnecessary redundancy, violations of dry principle (don’t repeat yourself).

instead, place function definitions before main.

that way easier see refers what, because functions used others come before other functions.

int main() {         int size;int array[size]; int sum=0; 

this should not compile, because in c++ dynamically allocated array can have size unknown @ compile time.

however, c99 supports “variable length arrays” a.k.a. vlas above syntax, , language extension g++ compiler supports that.

on third , gripping hand, g++ language extension above declares array of indeterminate length, because size variable has not been initialized , has indeterminate value.

with g++ compiler value 0, can other value.

to turn off g++ vla language extension, , other language extensions, use following g++ options:

 -pedantic -std=c++0x -wall 

for standard c++, instead of c99 vla should use c++ std::vector<int>.

in order declaration of std::vector class template, include standard library header <vector>.

   int index=0;    cout<<"enter size of array"<<endl;    cin>>size;                //enter size ofthe array... 

when you're using std::vector, here, knowing size, place declare vector.

or, if declared earlier, here place resize it.

   random_value(array, size); 

this better function returned vector of random values.

you use initialize declared vector.

   iterative_function (array, size, sum);     recursive_function ( size, array, index, sum);    getch(); 

regarding getch() call, see above comments <conio.h>.

   return 0; 

regarding value 0 here, see above comments <stdlib.h>.

}  int random_value(int array[], int size) {  cout<<"here value returned rand()"<<endl;    for(int i=0;i<size;i++)    { array[i]=( rand() % (0-2)); 

here have undefined behavior, accessing elements of possibly zero-size array.

     cout<<array[i]<<endl;    } }  int iterative_function (int array[], int size, int sum) {    int i,j, number, value; i=0;    cout<<"from iterative function"<<endl;    cout<<"------"<<endl;    for(i=0;i<size;i++)    sum=sum+array[i]; 

here again invoking undefined behavior, called “ub”, accessing non-existing array elements.

in addition, if array had been of non-zero size, has not been initialized , contain zeroes or arbitrary values (by holy standard called “indeterminate values”).

   cout<<"sum of array="<<sum<<endl;               getch(); 

see above comment <conio.h>.

   return 0;      //exit function. program terminated succesfully. } 

there no point in letting above function return same value. information-theoretical perspective, return value carries 0 bits of information. instead let function’s result value void.

int recursive_function ( int size, int array[], int index, int sum) {   if(size>index)   {       sum=sum+array[index];     index++;     recursive_function( size, array, index, sum);    } 

instead of incrementing index, non-idiomatic , therefore difficult spot experienced readers, use index + 1 in recursive call.

it idea add const every declaration possible.

that would, example, have forced use index + 1. :-)

  cout<<"from recursive function"<<endl;   cout<<"------"<<endl;   cout<<"new sum= "<< sum<<endl;    getch(); 

see above comment <conio.h>.

  return 0; 

see above comment function returning same value.

} 

summing up, undefined behavior happenstance if things appear work.

fix ub's (in particular replace c99 vla std::vector) first of all, perhaps ask new question if still not work should. ;-)