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true_smart@hotmail.com · Guest

I want use "for_each" to relpace the "for", following are my test code
segment.
class MapTestter
{
private:
long m_nTest;

public:
MapTestter(long n)
{
m_nTest = n;
}
~MapTestter()
{
int s = 0;
s++;
}
void print(int i)
{
std::cout< }
};

map
// I want to use "for_each" to relpace the "for"
for (long i = 0; i < 10; i++)
{
MapTestter *pNew = new MapTestter(i);
test.insert(make_pair(i, pNew));
}

// I want to use "for_each" to relpace the "for"
for (map test.end(); iter++)
{
(*iter).second->print(3);
}

for (map<long, MapTestter*>::iterator iter = test.begin(); iter !=
test.end(); iter++)
{
delete ((*iter).second);
}
How can I use "for_each"?

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Allan W · Guest

/**/ #include <iostream>
/**/ #include <map>
/**/ #include <algorithm>

/**/ //-- Here's your original MapTestter class
/**/ //-- (Misspelled? Try MapTester, no double-t)
/**/ class MapTestter {
/**/ private:
/**/ long m_nTest;
/**/ public:
/**/ MapTestter(long n) : m_nTest(n) {}
/**/ //-- Your destructor did nothing, so I removed it
/**/ void print(int i) { std::cout< /**/ };

/**/ //-- Here's your original map
/**/ std::map
/**/ //-- Here's a class I added that calls the print function for you.
/**/ class MapTestterPrinter {
/**/ int arg;
/**/ public:
/**/ MapTestterPrinter(int n) : arg(n) {}
/**/ void operator()(std::map<long, MapTestter*>::value_type m)
/**/ { m.second->print(arg); }
/**/ };

/**/ //-- Here's another one that calls delete for you
/**/ struct MapTestterDeleter {
/**/ void operator()(std::map<long, MapTestter*>::value_type m)
/**/ { delete m.second; }
/**/ };

/**/ int main() {
/**/ // I want to use "for_each" to relpace the "for"
/**/ for (long i = 0; i < 10; i++) {
/**/ MapTestter *pNew = new MapTestter(i);
/**/ test.insert(std::make_pair(i, pNew));
/**/ }
/**/ //-- That's not going to happen.
/**/ //-- So far, test is empty...
/**/ //-- Any use of for_each is going to result in 0 iterations

/**/ // I want to use "for_each" to relpace the "for"
/* /*-- This time, it IS possible.
/* for (std::map /* iter != test.end(); iter++)
/* {
/* (*iter).second->print(3);
/* } /*/
/**/ //-- Use a Functor class, MapTestterPrinter
/**/ MapTestterPrinter functor(3);
/**/ std::for_each(test.begin(), test.end(), functor);

/**/ /*-- Can do much the same thing here
/* for (std::map<long, MapTestter*>::iterator iter = test.begin();
/* iter != test.end(); iter++)
/* {
/* delete ((*iter).second);
/* } /*/
/**/ std::for_each(test.begin(), test.end(), MapTestterDeleter());
/**/ return 0;
}

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alexmdac@hotmail.com · Guest

std::map< A, B > theMap;

inline
void fn( std::pair< A, B > &mapEntry )
{
// do something here
}

// ...

std::for_each( theMap.begin(), theMap.end(), fn );

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