Solved

generating vectors on the fly

Posted on 2014-01-09
7
189 Views
Last Modified: 2014-01-31
Hi

Is it possible to generate vectors on the fly? I just need generic vectors that I then add to another  vector. I find it quite useless to create a vector and push into it  like
 std::vector<UINT64> temp;
temp.push_back(1);
temp.push_back(2);
temp.push_back(3);

 just so that i can  then add it to the enclosing vector.
enclosing_vector.push_back(temp);
temp.empty();
//add to temp again and push into enclosing_vector

I want to do something like this:
enclosing_vector.push_back(std::vector<UINT64> {1,2,3});

Is something more elegant possible?
0
Comment
Question by:LuckyLucks
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
7 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 39769184
You'd usually use 'vector::insert()' and an array for that, e.g.

UINT64 buf [] = {1,2,3};
size_t sz = sizeof(buf) / sizeof(UINT64);

enclosing_vector.insert(enclosing_vector.end(), buf, buf + sz);

Open in new window


Is that what you had in mind?
0
 

Author Comment

by:LuckyLucks
ID: 39775597
no, actually that is not what i wanted. I wanted a more elegant approach to do on the fly insertions into vectors (inserting vectors into vectors), without creating vector definitions for such a temporary use.

what you offered was another way of what i was doing in the first place and both are many lines of codes for a very simple purpose. I need something cleaner and more elegant if possible.
0
 
LVL 86

Expert Comment

by:jkr
ID: 39775601
Well, acting another vector to a vector still follows the same scheme, i.e.

std::vector<UINT64> temp;
temp.push_back(1);
temp.push_back(2);
temp.push_back(3);
enclosing_vector.(enclosing_vector.end(), temp.begin(), temp.end());

Open in new window


Sorry, but there does not seem to be a more elegant way (or I am completely missing the point).
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 86

Expert Comment

by:jkr
ID: 39808196
Sorry, but I can only guess that with your responsiveness, this is going to en dup nowhere since you are already posing new Qs about this: http://www.experts-exchange.com/Programming/Languages/CPP/Q_28346593.html

Can we cool down (or in your case heat up) to close that step by step?

And, as a HINT: Iteraction solves problems, not getting back half a weeek later. That is just plain frustrating.
0
 
LVL 32

Expert Comment

by:phoffric
ID: 39809457
>> I want to do something like this: ... std::vector<UINT64> {1,2,3}
You can overload the () operator (or another operator of your choosing) to do the push backs. Here is one approach.
class genVec : public vector<uint64_t>
{
public:
   genVec & operator () (uint64_t const & val)
   {
      this->push_back(val);
      return *this;
   }
};

int main() {
   genVec gv;
   gv(1)(2)(3);

Open in new window

0
 
LVL 32

Expert Comment

by:phoffric
ID: 39809476
I just noticed that you did not want to define explicit temporary vectors. gv is a temporary, but you don't have to use it:
   vector<genVec> enclosing_vector;
   genVec gv;
   gv(1)(2)(3);
   enclosing_vector.push_back(gv);
   enclosing_vector.push_back( genVec() );
   enclosing_vector.push_back( genVec() (4)(5)(6)(7) );

Open in new window

enclosing_vector now has a size of 3, and it's first element is a vector of size 3; 2nd element is a vector of size 0; 3rd vector is a vector of size 4.
0
 
LVL 32

Accepted Solution

by:
phoffric earned 500 total points
ID: 39809492
The parens are OK, but harder to type and not too stylish. You can change the () operator to, say, <<. I like this style better since it conveys the notion of pushing values to an object (like cout). Now you could write:
enclosing_vector.push_back( genVec() << 4 << 5 << 6 << 7 );

Open in new window

0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Often, when implementing a feature, you won't know how certain events should be handled at the point where they occur and you'd rather defer to the user of your function or class. For example, a XML parser will extract a tag from the source code, wh…
What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question