3 Download and installation

There are two NuGet packages of FParsec, which are built with different configuration options.

The basic package uses the Low‐Trust version of FParsec, which uses no unverifiable code and is optimized for maximum portability. The main limitation of this version is that any input stream is completely read into a string before parsing, which limits the maximum practical input size. This package also contains assemblies for .NET Standard 2.0.

The “Big Data edition” package uses the non‐Low‐Trust version of FParsec that is optimized for maximum performance and supports extremely large input streams. Since this configuration is also the default configuration of the solution files included with the source code, it is sometimes referred to as the “normal” version of FParsec. This version of FParsec does use “unsafe” (i.e. unverifiable) code involving unmanaged pointers. It also uses code generation in the implementation of isAnyOf, isNoneOf, anyOf, skipAnyOf, noneOf and skipNoneOf. Unfortunately, this version is currently not compatible with .NET Standard/.NET Core.

Should you measure a significant performance degradation when switching to the Big Data edition, you’re probably inadvertently recreating the same isAnyOf‐ or isNoneOf‐based parsers again and again, as explained here and here.

The .NET Framework assemblies in the NuGet packages are strongly signed. Their assembly version numbers will only be incremented for breaking changes. The .NET Standard assembly in the FParsec package is not signed.

The NuGet packages include PDBs and SourceLink support, which should allow you to step through FParsec code in the debugger of your IDE.

FParsec’s source code repository is hosted on GitHub at: github.com/stephan‐tolksdorf/fparsec

You can clone the source code using Git or you can download it as a zip‐file.

It’s an FParsec project policy to check only stable and tested code into the master branch of the GitHub repository, so you can normally just work with the master version of FParsec.

FParsec’s source code is written in both C# and F#. Since neither the C# nor the F# compiler directly support the other language, the respective components need to be built separately.

Hence, FParsec is built as two DLLs. The C# bits are compiled into the FParsecCS.dll and the F# bits (which depend on the C# bits) are compiled into FParsec.dll.

Projects that use FParsec thus have to reference both DLLs.

If you reference the DLLs in the F# Interactive console, you need to reference FParsecCS.dll before you reference FParsec.dll.

The solution file FParsec.sln in the root source folder and the associated project files in the subfolders can be used to build FParsec from the command line or with IDEs such as Visual Studio 2019 or JetBrains Rider.

To build the Low‐Trust version of FParsec, you have to specifiy either Debug-LowTrust or Release-LowTrust as the configuration. The Debug and Release configurations build the non‐Low‐Trust version of FParsec, which currently is not compatible with the .NET Core runtime.

The Test project in the solution files contains the unit tests for FParsec.

The file .vscode/tasks.json contains some convenient task definitions for Visual Studio Code.

The NuGet packages are built with the pack.ps1 PowerShell script.

For optimization reasons the normal implementation (the “Big Data edition”) of FParsec involves unverifiable code using unmanaged pointers and runtime code generation.

If you compile FParsec with the LOW_TRUST conditional compiler symbol, the unverifiable code is replaced with a “safe” alternative. This allows FParsec to be run in environments with “reduced trust”, such as medium trust ASP.NET applications, and it also allows FParsec to be compiled against reduced subsets of the .NET API.

In the Debug-LowTrust and Release-LowTrust configurations of the FParsec.sln solution file in the root source folder, LOW_TRUST is automatically defined as true.

You can configure FParsec’s source code with a number of conditional compilation symbols (a.k.a. preprocessor defines). Besides the Low‐Trust option, these symbols mostly serve tuning purposes.