CODEWITHSUNDEEP
c++sortingvector
Miek
Miek

Reputation: 1137

Sorting a vector of objects using a compare function

I am trying to follow a link where a someone is trying to simplify the C++ sort reference http://www.cplusplus.com/forum/beginner/4817/ however I can not get the bool operator function to compile the way he has it.

I have vector of event objects. I want to sort the vector based on the event begin time. If the begin times were numbers, this would be easier but they are strings so I had to write functions to convert to uint64_t, all of my code up to this sort attempt is working as it should. Here is the code I am trying to get to work:

The bool function:

bool EWriter:: operator () ( Event &a,  Event &b){
    return (stringToTime(stringReturnWrap(a.getBeginTime())) < stringToTime(stringReturnWrap(b.getBeginTime()))); 
}

This code compiles but I can not figure out how to give it a name, and therefore I cannot reference it in the sort. Also, I would rather overload the < operator but I keep getting an error it needs a third argument.

Here is my sort:

sort(events->begin(), events->end(), someFunctionName);??

Slightly unrelated is that I know I am supposed to use const in the args but I can not call the functions of the Event class if I have them implemented.

Upvotes: 0

Views: 272

Answers (2)

rendon
rendon

Reputation: 2363

You are overloading the parentheses operator:

bool EWriter:: operator () ( Event &a,  Event &b){
    return (stringToTime(stringReturnWrap(a.getBeginTime())) < stringToTime(stringReturnWrap(b.getBeginTime())));

}

Try with:

bool EWriter:: operator <( Event &a,  Event &b){
    return (stringToTime(stringReturnWrap(a.getBeginTime())) < stringToTime(stringReturnWrap(b.getBeginTime())));

}

Upvotes: 0

Drew Dormann
Drew Dormann

Reputation: 63745

By overloading operator(), you have made EWriter a functor.

Just pass it an instance of EWriter.

If EWriter has a default constructor, you can use:

sort(events->begin(), events->end(), EWriter());

Or pass it an EWriter that already exists.

Upvotes: 2

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