A common lisp wrapper for the openlibm mathematical library used by Julia. Openlibm is described as:
a high quality, system independent, portable, open source libm implementation
Until the project is in Quicklisp, you’ll need clone the repository
into your ~/common-lisp/ directory and then use quicklisp to load
it, like so (ql:quickload "libm").
If on MS Windows, the easiest way to obtain the library is with MSYS2 and then place the libopenlibm.dll file in the LIBM.CL directory. It can actually be in any directory on the %PATH%, but some people find that troublesome. On UNIX, you’ll likely install via a package manager and it will be the library will automatically be placed standard location for shared libraries.
LIBM.CL can be used as a reference to test the accuracy of a common lisp implementation. In my tests using CCL and MS Windows, the two agree to within 15 digits of accuracy for doubles. The most significant differences are in the single float functions. You can see the accuracy obtained in the tests.lisp file.
The library also contains a few functions that did not make it into the ANSI CL specification, notably log-gamma and gamma.
Finally, if you are interacting with numerical libraries that use IEEE-754, the C99 methods can be useful, for example in raising or detecting a NaN condition.
The library does not shadow CL, so you’ll need to specify the package when calling the functions, e.g. src_lisp{libm:acos}. Documentation for C99 is widespread. During development we referred to the Common mathematical functions and Complex number arithmetic pages. We do not wrap long double functions, since there is is only one lisp implementation that implements long double.
- %libm
This package contains bindings of the C99 functions as they appear in the C99 specification. This typically means multiple functions with different names doing the same thing, but varying in their argument types. E.g. cos, cosf, ccos and ccosf for doubles, floats, double complex and single float complex arguments respectively.
- %libm-complex
Complex numbers requires an additional FFI library, libffi. This library is used in a few languages for C bindings, most notably Python, but is a relatively recent addition to CFFI, and there a few bugs, for example in SBCL. For this reason we’ve made it a separate package whose symbols are reexported from %libm. This way you could create a version of libm without complex numbers if required.
- %libm-constants
These are the constants like LOG2E. They are included for completeness, but not exported symbols. The thinking is that if you are developing a numeric application in Common Lisp, you will likely have created your own constants package.
- libm
This is the package that most uses will want. It wraps the multiple C functions into a lisp-like call, dispatching on argument type. Handles complex numbers.
Mostly complete. There are a few functions, those requiring pointers, for example nan(char*) that haven’t been wrapped. There are examples for using pointers elsewhere in the code, if you need to wrap those functions.
When contributing to this repository, please first discuss major changes to the existing code you wish to make via issue. Minor changes and major additions are welcome. Please write good commit messages for pull requests.
LIBM.CL is available under the Microsoft Public License.