So here is my code for a sum function for a vector - using boolean success to just pretty much catch simple errors and what not
However when I compile it says that success is undeclared in my int main() and I was just wondering how to properly declare it in my main function
I know having success is kind of annoying - but it needs to be there

#include <iostream>
#include <vector>        // need this in order to use vectors in the program
using namespace std;

void computeSum (vector<int> &Vec, int  howMany, int total, bool success) 
//the computeSum function that will sum positive numbers in a vector
{
    success = true;
    total=0;
    if (success){
	for(int j=0;j < howMany;j++)
	    if (Vec[j] > 0){
		total+=Vec[j];
	    } else { 
		total+=Vec[j+1];
	    }
	cout << total;
    } else {
	cerr << "Oops!  Appears you cannot add up these numbers!";
    }
   
}

int main()
{
    vector<int> dataVec;

    int i, n, howMany, total;
    bool success=true;
    cout << "How many numbers would you like to put into the vector? \n";
    cin >> n; 

    dataVec.resize(n);

    for(vector<int>::size_type i=0;i < n;i++)
	{
	    cout << "Enter your number for " << i+1 << ": \n"; 
	    cin >> dataVec[i];
	}

    cout << "How many POSITIVE numbers would you like to sum? \n";
    cin >> howMany;
	cout << "Your total is: \n" << computeSum (dataVec, howMany, total, success);
    
}

Dani AI

Generated

Quick diagnosis: the compiler error you pasted (thanks for that, ) shows the real problem — you’re doing cout << computeSum(...) while computeSum is declared void. Streaming a void value is illegal, so the compiler complains about “no match for operator<< … void”. Also, because total and success are passed by value in your current prototype, changes inside the function don’t affect main, which explains why total in main never gets the value you think it does.

Two straightforward fixes (choose one):

  1. Make computeSum return the sum (and make success an output reference):

    int computeSum(const vector<int>& v, int howMany, bool& success) {
     if (howMany < 0 || howMany > (int)v.size()) { success = false; return 0; }
     success = true;
     int total = 0;
     for (int i = 0; i < howMany; ++i)
         if (v[i] > 0) total += v[i];
     return total;
    }
    // in main:
    int total = computeSum(dataVec, howMany, success);
    if (success) cout << "Your total is: " << total << '\n';
  2. Keep void but pass total and success by reference and don’t try to stream the function call:

    void computeSum(const vector<int>& v, int howMany, int& total, bool& success) { ... }
    computeSum(dataVec, howMany, total, success);
    cout << total;

Extra notes and cautions for :

  • Don’t use total += Vec[j+1] in the else branch — that will read past the end of the vector when j == howMany-1. Probably you meant to skip non-positive values or just ignore them.
  • Validate howMany <= dataVec.size() before looping and prefer const vector<int>& to avoid copying.
  • Keep computation and I/O separate: have the function compute and return (or write to refs) and let main handle printing.

Fixing the return/parameter semantics and the out-of-bounds logic will resolve the compiler error and the runtime risk.

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All 2 Replies

So here is my code for a sum function for a vector - using boolean success to just pretty much catch simple errors and what not
However when I compile it says that success is undeclared in my int main() and I was just wondering how to properly declare it in my main function
I know having success is kind of annoying - but it needs to be there

#include <iostream>
#include <vector>        // need this in order to use vectors in the program
using namespace std;

void computeSum (vector<int> &Vec, int  howMany, int total, bool success) 
//the computeSum function that will sum positive numbers in a vector
{
    success = true;
    total=0;
    if (success){
	for(int j=0;j < howMany;j++)
	    if (Vec[j] > 0){
		total+=Vec[j];
	    } else { 
		total+=Vec[j+1];
	    }
	cout << total;
    } else {
	cerr << "Oops!  Appears you cannot add up these numbers!";
    }
   
}

int main()
{
    vector<int> dataVec;

    int i, n, howMany, total;
    bool success=true;
    cout << "How many numbers would you like to put into the vector? \n";
    cin >> n; 

    dataVec.resize(n);

    for(vector<int>::size_type i=0;i < n;i++)
	{
	    cout << "Enter your number for " << i+1 << ": \n"; 
	    cin >> dataVec[i];
	}

    cout << "How many POSITIVE numbers would you like to sum? \n";
    cin >> howMany;
	cout << "Your total is: \n" << computeSum (dataVec, howMany, total, success);
    
}

success looks properly declared. Are you sure that's the problem? Cut and paste the exact compiler error.

success looks properly declared. Are you sure that's the problem? Cut and paste the exact compiler error.

Actually yeah I've noticed on this code I've declared it

bool success;

in my int main() however, when I compile it, it fgives me this crazy looking thing o.o

g++ -I/usr/local/include/bjarne/GUI -I -Wall -O3 -DNDEBUG -Wno-deprecated -o proj1
proj1.cc: In function ‘int main()’:
proj1.cc:52:76: error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits<char>]((* & std::cout), ((const char*)"Your total is ")) << computeSum((* & dataVec), howMany, total, ((int)success))’
proj1.cc:52:76: note: candidates are:
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:110:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:110:7: note: no known conversion for argument 1 from ‘void’ to ‘std::basic_ostream<char>::__ostream_type& (*)(std::basic_ostream<char>::__ostream_type&)’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:119:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type& (*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>, std::basic_ostream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:119:7: note: no known conversion for argument 1 from ‘void’ to ‘std::basic_ostream<char>::__ios_type& (*)(std::basic_ostream<char>::__ios_type&)’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:129:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:129:7: note: no known conversion for argument 1 from ‘void’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:167:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:167:7: note: no known conversion for argument 1 from ‘void’ to ‘long int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:171:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:171:7: note: no known conversion for argument 1 from ‘void’ to ‘long unsigned int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:175:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:175:7: note: no known conversion for argument 1 from ‘void’ to ‘bool’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:93:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:93:5: note: no known conversion for argument 1 from ‘void’ to ‘short int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:182:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:182:7: note: no known conversion for argument 1 from ‘void’ to ‘short unsigned int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:107:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:107:5: note: no known conversion for argument 1 from ‘void’ to ‘int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:193:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:193:7: note: no known conversion for argument 1 from ‘void’ to ‘unsigned int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:202:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:202:7: note: no known conversion for argument 1 from ‘void’ to ‘long long int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:206:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:206:7: note: no known conversion for argument 1 from ‘void’ to ‘long long unsigned int’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:211:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:211:7: note: no known conversion for argument 1 from ‘void’ to ‘double’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:215:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:215:7: note: no known conversion for argument 1 from ‘void’ to ‘float’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:223:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:223:7: note: no known conversion for argument 1 from ‘void’ to ‘long double’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:227:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:227:7: note: no known conversion for argument 1 from ‘void’ to ‘const void*’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:121:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:121:5: note: no known conversion for argument 1 from ‘void’ to ‘std::basic_ostream<char>::__streambuf_type*’
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/basic_string.h:2694:59: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:451:65: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:456:63: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:462:61: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:468:68: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:473:70: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:493:72: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/bits/ostream.tcc:323:70: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:510:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:523:75: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const signed char*)
/usr/lib/gcc/i686-redhat-linux/4.6.0/../../../../include/c++/4.6.0/ostream:528:77: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const unsigned char*)
make: *** [proj1] Error 1

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