Using c++ Lambda Expression

Question

I don't really understand Lambda expressions very well. I created a list that takes in a struct "brute";

typedef struct brute{
int entry;
string secWord;
string secHex;
}decrypt;

typedef list<brute*>Unsolved;

I then try to use the for_each to iterate through the list.

char combo[] = {'a','a','b','c');
std::for_each(unsolved.begin(), unsolved.end(),[&combo](int i )
{

});

[&combo} is what I'm trying to capture. I have 3 questions: is "int i" the iterator for the list? How do i access a member that is inside my unsolved list? Lastly do i need to define that my return value should be a char[]?

juanchopanza · Accepted Answer · 2013-03-06 21:53:30Z

3

std::for_each will expect a unary predicate that takes brute* or brute*&, something of the form

T foo(brute*);

would do. It ignores the return value. So your for_each call using a lambda could have this form:

std::array<char, 4> combo{'a','a','b','c'};
std::for_each(unsolved.begin(), unsolved.end(),[&combo](brute*& b) { .... } );

where I have used an std::array because it has simpler copy/assignment semantics than a plain array.

So, to answer the questions,

is "int i" the iterator for the list?

No

How do i access a member that is inside my unsolved list?

As shown in the example

Lastly do i need to define that my return value should be a char[]?

The return value gets ignored. If you need it then you need another algorithm.

edited Mar 6, 2013 at 21:53

answered Mar 6, 2013 at 21:48

juanchopanza

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