Calling Haskell from C#

Calling Haskell from C#

Here is a sample of how to call a Haskell function from C# using Haskell.NET:

  • Create a Haskell module that exports a function you want to call:
module MyModule where add :: Int -> Int -> Int add x y = x + y
  • Compile the Haskell module to a shared library (.so or .dll) using GHC:
ghc -dynamic -shared MyModule.hs -o MyModule.dll

Note that the -dynamic option is required to create a shared library that can be loaded by Haskell.NET.

  • Load the Haskell module and call the exported function from C#:
using System; using System.IO; using System.Reflection; using Haskell; class Program { static void Main(string[] args) { // Load the Haskell module var modulePath = Path.Combine(Environment.CurrentDirectory, "MyModule.dll"); var haskellAssembly = Assembly.LoadFrom(modulePath); var module = new HaskellModule("MyModule", haskellAssembly); // Call the exported function var add = module.GetFunction<int, int, int>("add"); var result = add(2, 3); Console.WriteLine("Result: {0}", result); } }

In this example, we first load the Haskell module using Assembly.LoadFrom(), passing in the path to the compiled DLL. We then create a HaskellModule object, passing in the name of the module and the loaded Assembly.

Next, we use HaskellModule.GetFunction() to retrieve a delegate that represents the exported add function. We can then call this delegate like any other C# function.

When we run the program, we should see the following output:

Result: 5

This demonstrates how to call a simple Haskell function from C# using Haskell.NET. For more information on using Haskell.NET, see the project's GitHub page: https://github.com/nessos/Haskell.NET

Examples

  1. "Calling Haskell DLL from C# example"

    • Code Implementation:
      [DllImport("YourHaskellLibrary.dll")] public static extern int YourHaskellFunction();
    • Description: Demonstrates using P/Invoke to call a Haskell function from a DLL in C#.

  2. "Interop C# with Haskell FFI"

    • Code Implementation:
      // Define a C wrapper function in Haskell foreign export ccall yourHaskellFunction :: IO CInt // In C# use P/Invoke to call the wrapper [DllImport("YourHaskellLibrary.dll")] public static extern int yourHaskellFunction();
    • Description: Shows how to create a C wrapper function in Haskell and call it from C# using P/Invoke.

  3. "C# Haskell interop using C libraries"

    • Code Implementation:
      [DllImport("YourCLibrary.dll", CallingConvention = CallingConvention.Cdecl)] public static extern int yourHaskellFunction();
    • Description: Illustrates calling a Haskell function that is wrapped in a C library from C#.

  4. "Using C# to call Haskell with parameters"

    • Code Implementation:
      [DllImport("YourHaskellLibrary.dll")] public static extern int YourHaskellFunction(int param1, double param2);
    • Description: Demonstrates passing parameters to a Haskell function from C# using P/Invoke.

  5. "C# Haskell interop with string parameters"

    • Code Implementation:
      [DllImport("YourHaskellLibrary.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)] public static extern IntPtr YourHaskellFunction(string str);
    • Description: Shows how to pass and receive string parameters between C# and Haskell using P/Invoke.

  6. "C# Haskell interop with structs"

    • Code Implementation:
      [StructLayout(LayoutKind.Sequential)] public struct YourStruct { public int Field1; public double Field2; } [DllImport("YourHaskellLibrary.dll")] public static extern int YourHaskellFunction(YourStruct yourStruct);
    • Description: Illustrates passing a struct between C# and Haskell using P/Invoke.

  7. "Calling Haskell functions with callbacks from C#"

    • Code Implementation:
      [UnmanagedFunctionPointer(CallingConvention.Cdecl)] public delegate void YourCallbackDelegate(int result); [DllImport("YourHaskellLibrary.dll")] public static extern void YourHaskellFunctionWithCallback(YourCallbackDelegate callback);
    • Description: Demonstrates calling Haskell functions that take callbacks from C#.

  8. "Marshalling Haskell data types in C#"

    • Code Implementation:
      [DllImport("YourHaskellLibrary.dll")] public static extern IntPtr YourHaskellFunctionReturningString(); string result = Marshal.PtrToStringAnsi(YourHaskellFunctionReturningString());
    • Description: Shows how to marshal Haskell data types (e.g., strings) in C# using P/Invoke.

  9. "C# Haskell interop with advanced types"

    • Code Implementation:
      [StructLayout(LayoutKind.Sequential)] public struct ComplexType { public int IntField; public IntPtr StringField; } [DllImport("YourHaskellLibrary.dll")] public static extern ComplexType YourHaskellFunctionWithComplexType();
    • Description: Illustrates interop with more complex data types between Haskell and C#.

  10. "C# Haskell interop error handling"

    • Code Implementation:
      [DllImport("YourHaskellLibrary.dll")] public static extern int YourHaskellFunction(); try { int result = YourHaskellFunction(); } catch (Exception ex) { // Handle exceptions }
    • Description: Demonstrates error handling when calling Haskell functions from C# and catching exceptions that may occur during the interop process.

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