CODEWITHSUNDEEP
c++
user3198219
user3198219

Reputation: 23

Getting the error:missing template arguments before '(' token

as homework we need to build a generic map that will work with a given unmodifiable code:

class startsWith {
    char val;
public:
    startsWith(char v) : val(v) {};
    bool operator()(const std::string& str) {
        return str.length() && char(str[0]) == val;
    }
};

void addThree(int& n) {
    n += 3;
}

int main() {
    Map<std::string, int> msi;
    msi.insert("Alice", 5);
    msi.insert("Bob", 8);
    msi.insert("Charlie", 0);

    // add To every name with B 3 points, using MapIf
    startsWith startWithB('B');
    MapIf(msi, startWithB, addThree);
}

I wrote:

template<typename T,  typename S,  typename Criteria,  typename Action>
class MapIf {
public:
    void operator() (Map<T,S>& map, Criteria criteria, Action act) {
        for (typename Map<T, S>::iterator iter = map.begin(); iter != map.end(); ++iter) {
            if (criteria(((*iter).retKey()))) {
                act(((*iter).retData()));
            }
        }
    }
};

and I get the error

Description Resource    Path    Location    Type
missing template arguments before '(' token main.cpp    ‪/ex4‬  line 46 C/C++ Problem

in the given code (in MapIf(msi, startWithB, addThree);)

How can I fix it? (I can only change my code)

Upvotes: 0

Views: 4887

Answers (1)

Simple
Simple

Reputation: 14390

It looks like MapIf should be a function, not a class:

template<typename T, typename S, typename Criteria, typename Action>
void MapIf(Map<T, S>& map, Criteria criteria, Action act)
{
    for (typename Map<T, S>::iterator iter = map.begin(); iter != map.end(); ++iter) {
        if (criteria(iter->retKey())) {
            act(iter->retData());
        }
    }
};

Upvotes: 3

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