CODEWITHSUNDEEP
c++arrayssortingstruct
lecardo
lecardo

Reputation: 1212

c++ trouble using sort for struct

I got a struct that a user can define what string values go in where. I've tried ordering it alphabetically but had no luck with what research I found online. I was hoping if one of use can see where im going wrong

libraries being used : iostream, string, fstream and algorithm

struct House
{
    int room_num;               
    string person;      
};

struct compare_by_word
{
    bool operator()(const House& lhs, const House& rhs)
    {
        return lhs.person < rhs.person;
    }
};

I get errors on this line, by the way im using visual studios 2010

  void asc_order()
    {
        sort(data.begin(), data.end(), compare_by_word());
//for loop will be displayed here to show table
    }

Errors I get:

Error: Identifier data is undefined

struct compare_by_word Error: type name is not allowed

Upvotes: 0

Views: 1102

Answers (4)

David G
David G

Reputation: 96810

You need to pass an instance of compare_by_word. This is done by calling its constructor:

std::sort(data.begin(), data.end(), compare_by_word());
//                                  ^^^^^^^^^^^^^^^^^

Live Demo

I also see that you're not compiling with any headers that introduce an object with a begin or end method. These are commonly used in vectors and other dynamic containers. So I think you should try passing the address range instead as feasible alternative:

std::size_t len = sizeof(data)/sizeof(*data);

std::sort(data, data + len, compare_by_word());

Live Demo

Or if you're compiling in C++11 you can pass a lambda callback in place of an explicit functor and use the begin and end library functions instead of the address range:

using std::begin;
using std::end;

std::sort(begin(data), end(data), [] (House const& lhs, House const& rhs)
{
    return lhs.person < rhs.person;
});

Live Demo

Upvotes: 1

Ritesh Kumar Gupta
Ritesh Kumar Gupta

Reputation: 5191

There is an error in sort statement.Replace it by:

sort(&data[0],&data[5],compare_by_word());

DEMO AT IDEONE

Upvotes: 0

user995502
user995502

Reputation:

An alternative would be

struct compare_by_word
{
    bool operator()(const House& lhs, const House& rhs)
    {
        return lhs.person < rhs.person;
    }
} compare_by_word;  // Here.

Upvotes: 0

SomeWittyUsername
SomeWittyUsername

Reputation: 18358

You're passing the type as comparator. You need to pass object of compare_by_word as comparator to sort.

Upvotes: 2

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