🔄 csd-cpp
Canonical Signed Digit (CSD) is a type of signed-digit representation of numbers. In CSD, each digit can only be -1, 0, or 1, and no two consecutive digits can be non-zero. This representation has the advantage of being unique and having a minimal number of non-zero digits. CSD is often used in digital signal processing applications, such as filter design, because it allows for efficient implementation of arithmetic operations using simple adders and subtractors. The number of adders/subtracters required to realize a CSD coefficient is one less than the number of nonzero digits in the library.
This library is all about converting numbers between decimal format and a special representation called Canonical Signed Digit (CSD). CSD is a way of writing numbers using only three symbols: 0, +, and -. It's particularly useful in certain areas of computer science and digital signal processing.
The main purpose of this library is to provide functions that can convert decimal numbers to CSD format and vice versa. It takes in regular decimal numbers (like 28.5 or -0.5) and converts them to CSD strings (like "+00-00.+" or "0.-"), and it can also do the reverse, taking CSD strings and converting them back to decimal numbers.
The library contains several functions, each with a specific role:
- to_csd: This function takes a decimal number and the number of decimal places desired, and outputs a CSD string. For example, it can convert 28.5 to "+00-00.+0" (with 2 decimal places).
- to_csd_i: Similar to to_csd, but it works specifically with integers. It converts whole numbers to CSD format without a decimal point.
- to_decimal_i and to_decimal: These functions do the opposite of to_csd. They take a CSD string and convert it back to a decimal number.
- to_csdnnz: This function is a variation of to_csd that allows you to specify the maximum number of non-zero digits in the result.
- to_csdnnz_i: This function is a variation of to_csd_i that allows you to specify the maximum number of non-zero digits in the result.
The library fulfills its intended function through a sequence of mathematical operations and logical tests. In order to effect a conversion from decimal to CSD, the system employs the use of powers of 2 in order to ascertain which of the three symbols (+, -, or 0) is to be used at each position within the CSD string. The algorithm then performs repeated divisions of the input number by two and compares the result to specific thresholds to determine the appropriate symbol to use.
In order to perform the conversion from CSD to decimal, the algorithm proceeds by multiplying the running total by 2 and then adding, subtracting, or performing no further action based on the value of the symbol in the CSD string. This is done for each symbol in the string, where the symbol values are +, -, or 0. A distinct logic is employed for the integral and fractional parts, respectively.
Furthermore, the library incorporates error-checking mechanisms to guarantee the exclusive utilisation of valid CSD symbols. It also furnishes comprehensive documentation and illustrative examples for each function, thus facilitating user comprehension of the operational procedures.
In conclusion, this library offers a comprehensive set of tools for working with CSD representations, facilitating the conversion between decimal and CSD formats in a variety of ways.
Used By
👀 See also
✨ Features
- Modern CMake practices
- Suited for single header libraries and projects of any scale
- Clean separation of library and executable code
- Integrated test suite
- Continuous integration via GitHub Actions
- Code coverage via codecov
- Code formatting enforced by clang-format and cmake-format via Format.cmake
- Reproducible dependency management via CPM.cmake
- Installable target with automatic versioning information and header generation via PackageProject.cmake
- Automatic documentation and deployment with Doxygen and GitHub Pages
- Support for sanitizer tools, and more
Usage
Adjust the template to your needs
- Use this repo as a template.
- Replace all occurrences of "Csd" in the relevant CMakeLists.txt with the name of your project
- Capitalization matters here:
Csdmeans the name of the project, whilecsdis used in file names. - Remember to rename the
include/csddirectory to use your project's lowercase name and update all relevant#includes accordingly.
- Capitalization matters here:
- Replace the source files with your own
- For header-only libraries: see the comments in CMakeLists.txt
- Add your project's codecov token to your project's github secrets under
CODECOV_TOKEN - Happy coding!
Eventually, you can remove any unused files, such as the standalone directory or irrelevant github workflows for your project. Feel free to replace the License with one suited for your project.
To cleanly separate the library and subproject code, the outer CMakeList.txt only defines the library itself while the tests and other subprojects are self-contained in their own directories. During development it is usually convenient to build all subprojects at once.
Build and run the standalone target
Use the following command to build and run the executable target.
Build and run test suite
Use the following commands from the project's root directory to run the test suite.
To collect code coverage information, run CMake with the -DENABLE_TEST_COVERAGE=1 option.
Run clang-format
Use the following commands from the project's root directory to check and fix C++ and CMake source style. This requires clang-format, cmake-format and pyyaml to be installed on the current system.
See Format.cmake for details. These dependencies can be easily installed using pip.
Build the documentation
The documentation is automatically built and published whenever a GitHub Release is created. To manually build documentation, call the following command.
To build the documentation locally, you will need Doxygen, jinja2 and Pygments installed on your system.
Build everything at once
The project also includes an all directory that allows building all targets at the same time. This is useful during development, as it exposes all subprojects to your IDE and avoids redundant builds of the library.
Additional tools
The test and standalone subprojects include the tools.cmake file which is used to import additional tools on-demand through CMake configuration arguments. The following are currently supported.
Sanitizers
Sanitizers can be enabled by configuring CMake with ‘-DUSE_SANITIZER=<Address | Memory | MemoryWithOrigins | Undefined | Thread | Leak | 'Address;Undefined’>`.
Static Analyzers
Static Analyzers can be enabled by setting -DUSE_STATIC_ANALYZER=<clang-tidy | iwyu | cppcheck>, or a combination of those in quotation marks, separated by semicolons. By default, analyzers will automatically find configuration files such as .clang-format. Additional arguments can be passed to the analyzers by setting the CLANG_TIDY_ARGS, IWYU_ARGS or CPPCHECK_ARGS variables.
Ccache
Ccache can be enabled by configuring with -DUSE_CCACHE=<ON | OFF>.
❓ FAQ
Can I use this for header-only libraries?
Yes, however you will need to change the library type to an INTERFACE library as documented in the CMakeLists.txt. See here for an example header-only library based on the template.
I don't need a standalone target / documentation. How can I get rid of it?
Simply remove the standalone / documentation directory and according github workflow file.
Can I build the standalone and tests at the same time? / How can I tell my IDE about all subprojects?
To keep the template modular, all subprojects derived from the library have been separated into their own CMake modules. This approach makes it trivial for third-party projects to re-use the projects library code. To allow IDEs to see the full scope of the project, the template includes the all directory that will create a single build for all subprojects. Use this as the main directory for best IDE support.
I see you are using
GLOBto add source files in CMakeLists.txt. Isn't that evil?
Glob is considered bad because any changes to the source file structure might not be automatically caught by CMake's builders and you will need to manually invoke CMake on changes. I personally prefer the GLOB solution for its simplicity, but feel free to change it to explicitly listing sources.
I want create additional targets that depend on my library. Should I modify the main CMakeLists to include them?
Avoid including derived projects from the libraries CMakeLists (even though it is a common sight in the C++ world), as this effectively inverts the dependency tree and makes the build system hard to reason about. Instead, create a new directory or project with a CMakeLists that adds the library as a dependency (e.g. like the standalone directory). Depending type it might make sense move these components into a separate repositories and reference a specific commit or version of the library. This has the advantage that individual libraries and components can be improved and updated independently.
You recommend to add external dependencies using CPM.cmake. Will this force users of my library to use CPM.cmake as well?
CPM.cmake should be invisible to library users as it's a self-contained CMake Script. If problems do arise, users can always opt-out by defining the CMake or env variable CPM_USE_LOCAL_PACKAGES, which will override all calls to CPMAddPackage with the according find_package call. This should also enable users to use the project with their favorite external C++ dependency manager, such as vcpkg or Conan.
Can I configure and build my project offline?
No internet connection is required for building the project, however when using CPM missing dependencies are downloaded at configure time. To avoid redundant downloads, it's highly recommended to set a CPM.cmake cache directory, e.g.: export CPM_SOURCE_CACHE=$HOME/.cache/CPM. This will enable shallow clones and allow offline configurations dependencies are already available in the cache.
Can I use CPack to create a package installer for my project?
As there are a lot of possible options and configurations, this is not (yet) in the scope of this template. See the CPack documentation for more information on setting up CPack installers.
This is too much, I just want to play with C++ code and test some libraries.
Perhaps the MiniCppStarter is something for you!
Related projects and alternatives
- ModernCppStarter & PVS-Studio Static Code Analyzer: Official instructions on how to use the ModernCppStarter with the PVS-Studio Static Code Analyzer.
- cpp-best-practices/gui_starter_template: A popular C++ starter project, created in 2017.
- filipdutescu/modern-cpp-template: A recent starter using a more traditional approach for CMake structure and dependency management.
- vector-of-bool/pitchfork: Pitchfork is a Set of C++ Project Conventions.
Star History (todo)
