Questions tagged [template-meta-programming]

For code that uses templates to generate compile-time executed code. For ordinary use of templates, use the 'template' tag instead.

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Template to unpack arguments to a std::function

I am writing some C++ code to interact with an external scripting language. I want to be able to register arbitrary C++ callable code as functions to be called from the script. The scripting library ...
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3 votes
1 answer
68 views

C++: Visit Any Type Holding Other Types (`std::any`, `std::variant`, etc.)

Intro I want to visit the value held by a class, which could be of multiple types. This class is very similar to a std::any, so I will be using this in this ...
2 votes
1 answer
82 views

C++17 view over the Ith elements of tuples in containers of tuples

For mainly didactic reasons, I have designed my ElementsView<I, T> class template, which provides a view over the I th ...
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1 vote
2 answers
50 views

C++ variardic universal template for unknown types, used to handle multiple network protocols

I am creating a template function with variardic arguments, to handle a specific classes that have some interface, method, member or whatever is specialized in a specialization area. However I came to ...
3 votes
1 answer
338 views

visit for std::any

While solving an online excersise I have written some basic implementation for a visit function that works with std::any. The ...
2 votes
1 answer
81 views

Binding move-only objects to functions (for a thread pool implementation)

I recently implemented a thread pool using std::functions. I only supported functions taking no arguments on the assumption that there would be no need to have them ...
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3 votes
1 answer
316 views

Mapping between Enum <-> Enum <-> String view

I've been working on some kind of mapper that would allow me to map between types. My objectives: it should allow mapping between two enums it should allow mapping enum to string_view it should allow ...
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2 votes
1 answer
134 views

An rough implementation of `std::is_constructible`

As a challenge/fun activity/task, I have implemented my version of std::is_constructible. Here is the source code: ...
2 votes
1 answer
116 views

Implementation of versatile IIR digital filter in C++

I have realized that all the digital filters of the IIR type have the same structure. They are described by difference equation in following form: $$ y(k) = b_0\cdot x(k) + b_1\cdot x(k-1) + \ldots +...
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2 votes
0 answers
70 views

invocable_traits v5

Goal: implement traits that for anything callable return its arity, return type and the argument types. Since pointers to data members are also callable, those should be handled (and be considered 0-...
1 vote
1 answer
72 views

invocable_traits v4

Update: there is a new version of this code: v5 is posted here Goal: implement traits that for anything callable return its arity, return type and the argument types. Since pointers to data members ...
3 votes
0 answers
44 views

invocable_traits v3

Update: there is a new version of this code: v4 is posted here Goal: implement traits that for anything callable return its arity, return type and the argument types. Since pointers to data members ...
3 votes
1 answer
51 views

invocable_traits

Update: there are new versions of this code: v3 is posted here and v4 is posted here Goal: implement traits that for anything callable return its arity, return type and the argument types. Since ...
2 votes
1 answer
245 views

c++20 compile time string utility v2

This is a follow up on c++20 compile time string utility, as suggested by G. Sliepen posted as a new question, so it can be reviewed on its own. The following code has suggested improvements from the ...
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4 votes
2 answers
1k views

c++20 compile time string utility

While upgrading some meta-program running in production for years to the latest (c++20) standard, I rewrote this particular compile time string utility. Even though this new version produces desired ...
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1 vote
2 answers
238 views

Automatically registering a class using header-only templated classes

I'm trying to reduce the boilerplate of a lot of header-only classes I'm using. Each of these classes must go through a registration step. I want this step to be defined in the same file as the class ...
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1 vote
1 answer
54 views

One-time dynamic, many-time *almost* static type dispatch

Annoyed at the tension between good software design principles that require well-defined delimitations between interface and implementations, and the requirements for critical code to run fast, which ...
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8 votes
3 answers
2k views

C++17 : Typelist manipulation

I'm reading "Modern C++ Design"(A. Alexandrescu, 2002) and practicing basic TMP in chapter 3. Typelists. Since the book is quite dated, I revised example codes in C++17-esque manner. Feel ...
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1 vote
1 answer
306 views

template function for conditional dereference

I don't know why there's no such function in std (at least I didn't find one). I need a conditional template function to return a reference to an object of T. ...
3 votes
1 answer
508 views

Object to ignore unused function output parameters

In our software we have some functions that return information through lvalue reference parameters, which, in some cases, are irrelevant for the calling code. For that reason, I tried to come up with ...
1 vote
1 answer
131 views

Handle C++ templates in Qt5

Searching for a solution to my problem I've read many posts regarding templates in Qt (including those on SE) and didn't find a complete solution (or I should say a complete example of a solution) so ...
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6 votes
1 answer
314 views

Implementing apply_each for tuple c++

I'm implementing apply_each for tuple-like object as a general function which may be a combined version of for_each and ...
2 votes
1 answer
102 views

Creating a structural type array wrapper to be qualified as non-type template parameter C++

I'm trying to replicate std::array but with modifications that I should put the private data member to the public so the class template ...
2 votes
1 answer
82 views

Computing nth Tribonacci number at compile time using C++ template metaprogramming facilities

I have this small C++ program for computing the \$n\$th Tribonacci number at compile-time. My main concern is: is it possible to get rid of the statickeyword (I had ...
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1 vote
1 answer
109 views

A multi key/value type "folded" map class template

I have recently come across a use case where I need to lump many maps into a single container. These maps can have different combinations of key/value types, but they all differ from one another. For ...
4 votes
3 answers
2k views

De-/Serialization of structs representing TCP messages

I wrote two template functions to serialize and deserialize structs representing messages to be sent and received via a TCP socket: ...
2 votes
0 answers
101 views

Generic way to access private/protected members

Motivation I and the company is working on building C++ SDK automatically for several platforms, including Windows. In summary, I have to test somehow if the private member of function pointers' type ...
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5 votes
3 answers
746 views

C++ Generic Callback class with removable listeners by unique id

I'm quite new to the STL. Does this make sense? Is there a better way of removing the listeners instead of using shared_ptr while keeping the code short and simple? Is there something in the STL to ...
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3 votes
1 answer
149 views

Implementation of the basic matrix operations for embedded application in C++

I have been developing a control software in C++ and for implementation of the control algorithms I need basic matrix operations like addition, subtraction, multiplication and multiplication by scalar....
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1 vote
0 answers
136 views

"tuple with named fields" implementation

I'd like to show you a type I made while experimenting with literal, non-type template parameters in C++20. The idea is to provide a type that wraps up tuple-like types (std::tuple, std::pair, even ...
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2 votes
1 answer
739 views

C++ generic, multi-dimensional linear interpolation template

Use-case in a nutshell: Interpolate fixed-sized data (a lookup table) that provides output values for combinations of a (fixed) number of inputs. The appropriate scaling is done externally, each axis ...
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5 votes
1 answer
292 views

Binary IO inspired by struct pack

About I'm writing a header-only template library for helping with binary IO. It is inspired by pack-d, which is in turn inspired by Python's struct module. I've only finished the output part and ...
1 vote
0 answers
131 views

Making std::optional a monad via SFINAE

To practice with SFINAE, template meta programming, functional programming and monads in C++, I decided to try writing a skinny version of the two functions (monadic binding and return) that make <...
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4 votes
3 answers
382 views

Calculate the centroid of a collection of complex numbers

In working on another problem, one component I needed was to calculate the centroid of a collection of complex objects. The well-known way to calculate this is to simply average the real and ...
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0 votes
2 answers
2k views

struct,template arguments, C++ [closed]

I am writing color model logic in C++. I ask review in defining limits for the color model, by saying Limits I mean this. Consider a struct which represents ...
6 votes
1 answer
304 views

Using templates to wrap variardic JNI method calls into type-safe C++ functors

I am working on a project which uses JNI. More than once I fell over the absence of type safety working with the variardic function calls. So I came up with this module. It wraps the variardic JNI ...
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2 votes
1 answer
40 views

Colour-model classes using CRTP

I want to implement color space logic. So I started with creating some structs: ...
7 votes
1 answer
285 views

Generic test case templates

I often find that when I am writing, refactoring, or reviewing code that I want to do some simple testing. There are many existing test frameworks such as gtest and cppunit but my desire was to ...
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4 votes
1 answer
206 views

Template Metaprogramming and Modular Arithmetic

Story I'm trying to become more familiar with template metaprogramming and practice more of it. I need to use modular arithmetic to solve certain problems and so I decided to write a general purpose ...
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5 votes
1 answer
110 views

Compiletime (constexpr) Differential Equation System Description for use in Optimal Control

Background In the field of optimal control, it is part of everyday business to solve ordinary differential equations numerically. A differential equation system or dynamic system describes e.g. the ...
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4 votes
1 answer
343 views

Template Metaprogramming - Multidimensional Vector Declaration

[EDIT] The question has been edited. Please make sure to read the summary at the end of the post. If you'd like me to make a new post with a cleaner explanation and better examples, tell me to do so ...
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9 votes
2 answers
1k views

How to simplify this C++ CRTP example?

I wanted a simple thing: being able to override a base class and just add one single getter. The bad thing is the base class does override some operators and will return the wrong type. I, therefore, ...
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7 votes
2 answers
164 views

constexpr Precalculate size of serialized data with templates and C++20 concepts

Im writing a serializer that will do serialization/deserialization as fast as possible, and that uses templates so that i dont have to create a ton of functions for every data structure, This is the ...
4 votes
1 answer
183 views

Polynomial library using expression templates

In a recent toy project, I made heavy use of calculations involving polynomials in Z[x]. As an experiment, I decided to try out implementing expression templates - and it did seem to provide drastic ...
5 votes
1 answer
373 views

Using SFINAE to provide "default" output operators

I am an undergraduate CS student trying to implement simple unit test framework on C++ as a pet project. The framework has an assertion macro like ...
3 votes
1 answer
165 views

Const wrapper for iterator

Edit: added clarification for why I want this, and updated the code since I don't have any answers yet I have a C++11 array-like class which (can be) a wrapper around a random-access iterator. Index-...
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4 votes
1 answer
340 views

slab malloc/free implementation

I'm trying to implment memory allocator guided by this tutorial. I used a mix of Next-fit search and Segregated-list search. There are multiple slabs of different sizes (a slab is contagious blocks of ...
3 votes
1 answer
166 views

Haskell-like function composition function

Much like this question I'm attempting to write in C++ something which can resemble Haskell's (.) function as much as possible, which is basically Chapter 1's ...
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3 votes
0 answers
50 views

Getting around gsl/span's restriction on temporaries

The goal of this code is to allow temporary RHS variables to be used in a span, specifically as an argument to a function, to be deleted later after the function completes, allowing the passing of ...
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5 votes
1 answer
173 views

Meta functions for sequences of exponents of 2

I have implemented some meta functions to create sequence for exponents of 2. I would love to know if there is any way to make the code more optimized. Note: ...
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