ordered-map | C++ hash map and hash set which preserve the order | Hashing library

by Tessil C++ Version: v1.1.0 License: MIT

X-Ray Key Features Code Snippets Community Discussions(10)Vulnerabilities Install Support

kandi X-RAY | ordered-map Summary

ordered-map is a C++ library typically used in Security, Hashing applications. ordered-map has no bugs, it has no vulnerabilities, it has a Permissive License and it has low support. You can download it from GitHub.

C++ hash map and hash set which preserve the order of insertion

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Security

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ordered-map has a low active ecosystem.

It has 415 star(s) with 56 fork(s). There are 26 watchers for this library.

It had no major release in the last 12 months.

There are 4 open issues and 19 have been closed. On average issues are closed in 13 days. There are no pull requests.

It has a neutral sentiment in the developer community.

The latest version of ordered-map is v1.1.0

Quality

ordered-map has 0 bugs and 0 code smells.

Security

ordered-map has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.

ordered-map code analysis shows 0 unresolved vulnerabilities.

There are 0 security hotspots that need review.

License

ordered-map is licensed under the MIT License. This license is Permissive.

Permissive licenses have the least restrictions, and you can use them in most projects.

Reuse

ordered-map releases are available to install and integrate.

Installation instructions, examples and code snippets are available.

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ordered-map Key Features

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ordered-map Examples and Code Snippets

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Community Discussions

Trending Discussions on ordered-map

Is there any possibility that std::unordered_map collides?

Emplace a std::array of non-movable objects that cannot be default constructed

Qt: how to implement a hash function for QColor?

Why do I need to declare a default constructor in order to compile when returning an unordered_map value?

Emscripten: fatal error: 'tr1/unordered_map' file not found

Can I use lambda as a hashing function in boost::multi_index hash-like interface?

unordered_map MSVC invalidation guarantee

C++: How can I pass keys and values into a constructor to make a map without copying the values of the map during construction?

unordered_map excess calls to hash function

Why does iterating unordered::map and adding new elements does not lead to an infinte loop?

QUESTION

Is there any possibility that std::unordered_map collides?

Asked 2022-Jan-21 at 20:36

I seen a post in here that you could "meet with the Birthday problem." while using std::unordered_map

When should I use unordered_map and not std::map

Which really surprises me, that is the same that saying std::unordered_map is unsafe to use. Is that true? If i'm not explaining myself, let me show you an example:

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ANSWER

Answered 2022-Jan-21 at 20:36

Is there any possibility that std::unordered_map collides?

It isn't the container that has collisions, but the hash function that you provide for the container.

And yes, all hash functions - when their output range is smaller than the input domain - have collisions.

is there any possibility that it prints ERROR!?

No, it isn't possible. It's completely normal for the hash function to put multiple values into a single bucket. That will happen in case of hash collision, but it also happens with different hash values. The lookup function will get the correct value using linear search. The identity of a key is determined by the equality function, not by the hash function.

Source https://stackoverflow.com/questions/70807246

QUESTION

Emplace a std::array of non-movable objects that cannot be default constructed

Asked 2021-Dec-08 at 09:45

I have a class that contains a std::mutex so it is not movable or copiable.

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ANSWER

Answered 2021-Dec-08 at 09:45

With custom array, you might do

Source https://stackoverflow.com/questions/70270749

QUESTION

Qt: how to implement a hash function for QColor?

Asked 2021-Nov-30 at 21:15

I have a need to use std::pair as a key of unordered_map. As for the pair, I know that there is boost functionality that can be used, but what about the color? Is it enough to just provide the hash template in the std namespace? If so, what would be the best attribute of the color to base the hash on to maximize the performance and minimize collisions? My first thought was about simple name(). If so

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ANSWER

Answered 2021-Nov-30 at 21:15

What you propose will probably work (although you would have to convert the color name from QString to std::string), I would use the RGBA value of the color directly. It is a bit cheaper than having to go through the QString to std::string construction and hash calculation:

Source https://stackoverflow.com/questions/70175131

QUESTION

Why do I need to declare a default constructor in order to compile when returning an unordered_map value?

Asked 2021-Mar-29 at 22:34

This example fails to compile unless I uncomment the default constructor declaration:

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ANSWER

Answered 2021-Mar-29 at 22:34

When the compiler compiles this line:

Source https://stackoverflow.com/questions/66862274

QUESTION

Emscripten: fatal error: 'tr1/unordered_map' file not found

Asked 2021-Mar-19 at 14:46

So I am trying to compile the following code using emscripten:

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ANSWER

Answered 2021-Mar-19 at 14:46

Why is this file not found by emcc? Is there an alternate way to handle unordered_maps in C++?

Because it moved to in 2011.

If it is in neither place, you have a very old clang, and it has no unordered_map.

Source https://stackoverflow.com/questions/66709398

QUESTION

Can I use lambda as a hashing function in boost::multi_index hash-like interface?

Asked 2020-Dec-24 at 08:21

Is it possible to use lambda for hashing in hashed__unique interface for boost::multi_index? See this example: https://godbolt.org/z/1voof3

I also saw this: How to use lambda function as hash function in unordered_map? where the answer says:

You need to pass lambda object to unordered_map constructor since lambda types are not default constructible.

and I'm not sure is it even possible to do for the given example on godbolt.

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ANSWER

Answered 2020-Dec-24 at 00:20

I don't think you can. With a standard container you would have had to supply the actual instance to the constructor. However, MultiIndex doesn't afford that:

docs

As explained in the index concepts section, indices do not have public constructors or destructors. Assignment, on the other hand, is provided. Upon construction, max_load_factor() is 1.0.

Loophole?

You can perhaps get away with a locally defined class:

Source https://stackoverflow.com/questions/65432195

QUESTION

unordered_map MSVC invalidation guarantee

Asked 2020-Dec-17 at 23:10

At https://docs.microsoft.com/en-us/cpp/standard-library/unordered-map-class?view=msvc-160 MS states:

"inserting an element invalidates no iterators"

But the book "The C++ Standard Library" by Nicolai Josuttis and https://en.cppreference.com/w/cpp/container/unordered_map both state that insert may invalidate iterators if insert causes a rehash.

Is MS simply providing a stronger guarantee than the standard? If so, are implementations allowed to do such things?

thanks, Marc

...

ANSWER

Answered 2020-Dec-17 at 23:10

Yes, each compiler vendor must at the minimum comply with the guarantees of the standard, however they are free to offer stronger guarantees if they so choose. For example, all compilers worth their salt guaranteed return value optimization (RVO) long before the standard mandated it.

Source https://stackoverflow.com/questions/65349598

QUESTION

C++: How can I pass keys and values into a constructor to make a map without copying the values of the map during construction?

Asked 2020-Oct-20 at 21:14

Here is a minimal example where an object of type WrapMap contains an unordered_map. The only thing that will change in the map is the values, not the length and not the keys.

However, I have found that each value passed into each pair is copied twice. By using move, it seems to have reduced the number of copies by 1 (although the move doesn't show up in the output, so maybe I've done something wrong).

...

ANSWER

Answered 2020-Oct-20 at 21:14

emplace

You can use the emplace member function of unordered_map:

Inserts a new element into the container constructed in-place with the given args if there is no element with the key in the container.

Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations. The constructor of the new element (i.e. std::pair) is called with exactly the same arguments as supplied to emplace, forwarded via std::forward(args).... [...]

Source https://stackoverflow.com/questions/64453283

QUESTION

unordered_map excess calls to hash function

Asked 2020-Sep-10 at 07:00

The following code results with unexplained calls to the hash function:

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ANSWER

Answered 2020-Jul-22 at 19:32

I can't explain why it is done that way, but it doesn't fit in a comment, so I leave it here in the answer section. You have two parts in the stdlib (10.1.0) upon insertion of an element:

Source https://stackoverflow.com/questions/63041408

QUESTION

Why does iterating unordered::map and adding new elements does not lead to an infinte loop?

Asked 2020-Aug-16 at 06:40

I am iterating through a std::unordered_map

...

ANSWER

Answered 2020-Aug-16 at 06:40

Inserting new elements invalidates your iterators at some point, however, you use them again, hence UB

For details, See Iterator invalidation rules and iterator invalidation in map C++

To see such behavior, use the following code

Source https://stackoverflow.com/questions/63431466

Community Discussions, Code Snippets contain sources that include Stack Exchange Network

Vulnerabilities

No vulnerabilities reported

Install ordered-map

To use ordered-map, just add the include directory to your include path. It is a header-only library. If you use CMake, you can also use the tsl::ordered_map exported target from the CMakeLists.txt with target_link_libraries. If the project has been installed through make install, you can also use find_package(tsl-ordered-map REQUIRED) instead of add_subdirectory. The code should work with any C++11 standard-compliant compiler and has been tested with GCC 4.8.4, Clang 3.5.0 and Visual Studio 2015. To run the tests you will need the Boost Test library and CMake.

Support

For any new features, suggestions and bugs create an issue on GitHub. If you have any questions check and ask questions on community page Stack Overflow .

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