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c++searchlambda
user1038502
user1038502

Reputation: 837

Searching in a list of structs with lambda-like syntax in C++

struct Data
{
int Id;
std::vector<int> SomeData
}

std::vector<Data> dataList = ....

int wantedIndex = 11;
std::find(dataList.begin(), dataList.end(), "where dataList.Id == wantedIndex")

Is this syntax possible in standard C++ in some way in Visual Studio 2008?

Upvotes: 0

Views: 730

Answers (3)

A. K.
A. K.

Reputation: 38126

Well if you have visual studio 2008 then you cannot use lambda function i guess The proper way to do is following:

int wanted_index = 11;
struct Data
{
int Id;
std::vector<int> SomeData
}
bool find_fun(int i)
{ 
 return i == wanted_index;
}
//std::vector<Data> dataList = ....

std::find(dataList.begin(), dataList.end(), find_fun);

You can also use boost bind or std::tr1 bind to have lambda function like syntax. As it appears from the msdn visual studio 2008 documentation that you can use std::bind() also see: http://msdn.microsoft.com/en-us/library/bb982702(v=vs.90).aspx

so you can use :

bool find_fun1(int i, int wanted_index)
{
  return i == wanted_index
}
int wanted_index = 11;
std::find_if(dataList.begin(), dataList.end(), std::bind(find_fun1,_1,wanted_index));

Upvotes: 1

mkaes
mkaes

Reputation: 14119

If you cannot use C++11. Maybe you can use boost phoenix.

It would be like this:

#include <boost\phoenix\phoenix.hpp>
...
std::find_if(dataList.begin(), dataList.end(), 
boost::phoenix::bind(&Data::Id, boost::phoenix::placeholders::arg1) == boost::phoenix::val(wantedIndex)));

Although I think in your very simple case bind from boost will also do it.

std::find_if(dataList.begin(), dataList.end(), boost::bind(&Data::Id, _1) == wantedIndex);

Upvotes: 2

pmr
pmr

Reputation: 59811

C++11 comes with support for lambdas:

std::find_if(dataList.begin(), dataList.end(), 
             [&wantedIndex](const Data& x) { return x.Id == wantedIndex;});

Upvotes: 1

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