How To Use Search (Template) in algorithms??

[Neerad]

Any body knows how is search template to be used which is declaed in algorithms??

[Philip Nicoletti]

Here is a simple example. Maybe if you give a brief
description of your problem, more info can be provided.
(might use find() instead of search(), etc.)


#include <iostream>
#include <list>
#include <vector>
#include <algorithm>

using namespace std;


int main()
{
list<int> mylist;
mylist.push_back(1);
mylist.push_back(4);
mylist.push_back(2);
mylist.push_back(5);
mylist.push_back(7);

vector<int> myvector;
myvector.push_back(2);
myvector.push_back(5);

//
// check if "myvector" is in "mylist"
//

list<int>::iterator pos;

pos = search(mylist.begin(),mylist.end(),myvector.begin(),myvector.end());

//
//

if (pos != mylist.end())
{
cout << "myvector found in mylist starting with element ";
cout << distance(mylist.begin(),pos) + 1 << endl; // maybe not use "+1" ?
}
else
{
cout << "myvector not found in mylist" << endl;
}


return 0;
}

[Neerad]

Thanks a lot buddy,

The problem was that i read the MSDN which explained in the following way

search
template<class FwdIt1, class FwdIt2>
FwdIt1 search(FwdIt1 first1, FwdIt1 last1,
FwdIt2 first2, FwdIt2 last2);
template<class FwdIt1, class FwdIt2, class Pred>
FwdIt1 search(FwdIt1 first1, FwdIt1 last1,
FwdIt2 first2, FwdIt2 last2, Pred pr);
The first template function determines the lowest value of N in the range [0, (last1 - first1) - (last2 - first2)) such that for each M in the range [0, last2 - first2), the predicate *(first1 + N + M) == *(first2 + M) is true. It then returns first1 + N. If no such value exists, the function returns last1. It evaluates the predicate (last2 - first2) * (last1 - first1) times, at most.

The second template function behaves the same, except that the predicate is pr(*(first1 + N + M), *(first2 + M)).

My problem was to comprehend the above language. I would still like to understand it (if someone help me out). The very first thing is 'predicate' which is not understood.

Thanx buddy.
Neerad

[Graham]

A predicate is simply a function (or function object) that returns a bool. So, the following are predicates:

bool less(int i, int j)
{
return i < j;
}

class UnaryPredicate
{
public:
UnaryPredicate(int val) : value_(val) {}
bool operator()(int i)
{
return i == value_;
}
private:
int value;
};

A binary predicate takes two arguments, and a unary predicate takes one argument. The STL defines lots of predicates for you: less<>, greater<>, not<> and so on.

The MSDN descriptions of the algorithms are particularly awful. I would suggest that you invest in a good STL book (Josuttis or Austern are both worth reading) if you're going to be using STL in any great amount.

[Neerad]

Thanx buddy,

This methametics will some day kill me. I gotta start doing some maths again right from grade 5 onwards!

Thanx a lot.