Variables not declared in this scope

The problem lies within the block:

check_sort(l.begin(), l.end(), "list");
time_insert(insert_list, data);
check_sort(s.begin(), s.end(), "set");
time_insert(insert_set, data);
check_sort(v.begin(), v.end(), "vector");
time_insert(insert_vector, data);

The error states that the variables are not declared in the scope, but shouldn't l,s,v be universal variables here? What am I doing wrong.

#include <cmath>
#include <iterator>
#include <iostream>
#include <iomanip>
#include <vector>
#include <ctime>
#include <list>
#include <set>
#include <algorithm>
#include <cstdlib>

using namespace std;

typedef void Inserter(vector<double>);

vector<double>开发者_StackOverflow中文版; gen_data(int num_elts);
void insert_list(vector<double> data);
void insert_set(vector<double> data);
void insert_vector(vector<double> data);

void time_insert( Inserter inserter, vector<double> data);

template <class Iter> bool is_sorted(Iter first, Iter last);
template <class Iter> void check_sort(Iter first, Iter last, string cont_kind);

int main() {
    srand(time(0));// initialize random number generator
    cout << "How many elements for container? ";
    int num_elts = 0;

    while (cin >> num_elts) {
    if (num_elts <= 0)
        cout << "Error, should be > 1";
    else {
        vector<double> data = gen_data(num_elts);

        check_sort(l.begin(), l.end(), "list");
        time_insert(insert_list, data);
        check_sort(s.begin(), s.end(), "set");
        time_insert(insert_set, data);
        check_sort(v.begin(), v.end(), "vector");
        time_insert(insert_vector, data);

    }
    cout << "\nHow many elements for next container? ";

    }
    return 0;

} 
void time_insert( Inserter inserter, vector<double> data) {
    clock_t t1 = clock();
    if (t1 == clock_t(-1)) { //if clock() doesn’t work
    cerr << "sorry, no clock\n";
    exit(1);
    }

    inserter(data);
    clock_t t2 = clock(); 
    if (t2 == clock_t(-1)) {
    cerr << "sorry, clock overflow\n";

    exit(2);
    }

    cout << "Elapsed time: " << fixed << setprecision(2)
     << double(t2-t1)/CLOCKS_PER_SEC << " seconds\n";

}

class Larger_than { 
    double v;
public: 
    Larger_than(double vv) : v(vv){}
    bool operator()(double x) const {return x>v;}
};

// Sorts and then inserts data into a list
void insert_list(vector<double> data)
{
    list<double> l;
    for(int i=0; i < data.size(); i++){
    list<double>::iterator p = find_if(l.begin(),l.end(), Larger_than(data[i]));
    l.insert(p, data[i]);
    }
} 
// Sorts and then inserts data into a list
void insert_set(vector<double> data)
{
    set<double> s; 
    for(int i=0; i < data.size(); i++){
    set<double>::iterator p = find_if(s.begin(),s.end(), Larger_than(data[i]
                          ));
    s.insert(p, data[i]);
    }
} 
// Sorts and then inserts data into a list 
void insert_vector(vector<double> data)
{
    vector<double> v; 
    for(int i=0; i < data.size(); i++){
    vector<double>::iterator p = find_if(v.begin(),v.end(), Larger_than(data
                                        [i]));
    v.insert(p, data[i]);
    }
} 

// generate num_elts random numbers in the range [0.0, 1.0), 
// which are returned in a vector

vector<double> gen_data (int num_elts) 
{
    vector<double> result; 
    for (int i = 0; i < num_elts; i++) {
    double datum = 1.0*rand()/RAND_MAX; 
    result.push_back(datum);
    }
    return result;
}

// is container spanned by [from, last) sorted?  
template <class Iter> bool is_sorted(Iter first, Iter last)  
{  
    Iter next = first;                   // next element  
    for (next++; next != last; next++, first++) {  
    if (*first > *next)  
        return false;  
    }  
    return true;  
}  

// prints a msg describing container kind, as well as whether container  
// spanned by [from, last) is sorted  
template <class Iter> void check_sort(Iter first, Iter last, string cont_kind)  
{  
    cout << "Check: " << cont_kind << " is ";  
    if (!is_sorted(first, last)) cout << "not ";  
    cout << "sorted\n";  
} 

How should main know about s, l and v at all? They're local variables of completely unrelated functions (the insert_xxx ones), there's no way main could know about them. If you want to make them globally accessible, just make them global variables, i.e., put their definition before main:

// ...

list<double> l;
set<double> s;
vector<double> v;

int main(){
  // ....
}

// ...

It looks like l is defined in the 'insert_list' function and would not available in main. Only variables defined insider your function are available.

You don't appear to have declared the variables at all. Why do you think they should exist in main? There are no globals or locals with those names anywhere that I can see. Try declaring them before using them.