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README.md

SageFs Samples

Learn F# interactively with SageFs! Each sample is a proper .NET project you can open, build, and run — or use SageFs for instant inline feedback.

Quick Start

# Run the F# Koans (22 exercises, 162 tests):
cd samples/from-koans/SageFs.Samples.Koans
dotnet run

# Or use SageFs for live feedback: start the daemon, then create a session
# for the project from your editor, the dashboard or an MCP client.
sagefs

Sample Projects

🧘 F# Koans — Learn F# from Scratch

22 progressive exercises teaching F# fundamentals — from let bindings to discriminated unions and data pipelines. Adapted from FSharpKoans for SageFs.

from-koans/SageFs.Samples.Koans/     162 tests

🌉 Language Bridges — Coming from Another Language?

Each bridge shows F# equivalents for patterns you already know. Pick the one that matches your background:

from-csharp/SageFs.Samples.FromCSharp/          11 tests
from-python/SageFs.Samples.FromPython/          15 tests
from-java/SageFs.Samples.FromJava/              11 tests
from-javascript/SageFs.Samples.FromJavaScript/  18 tests
from-rust/SageFs.Samples.FromRust/              18 tests
from-jupyter/SageFs.Samples.FromJupyter/        12 tests

🎮 Demos — Real Applications

Working applications demonstrating SageFs capabilities:

demos/SageFs.Samples.RaylibHello/      Raylib graphics — animated shapes
demos/SageFs.Samples.RaylibGame/       Raylib game — star catcher with scoring
demos/SageFs.Samples.WebappDatastar/   Falco web app — reactive todo list

Running the Projects

Option 1: dotnet run (simplest)

cd samples/from-koans/SageFs.Samples.Koans
dotnet run

Test projects show Expecto results in the terminal. Demo projects launch their application (Raylib window or web server).

Option 2: SageFs (best experience)

sagefs
# then, from your editor, the dashboard or an MCP client, create a session for
# samples/from-koans/SageFs.Samples.Koans/SageFs.Samples.Koans.fsproj

With SageFs, you get:

  • ✓/✗ gutter markers next to each test
  • Alt+Enter on any expression for inline results
  • Live feedback as you edit. On my machine, with the small FromCSharp sample, the verdict on the edited function's test arrives about 0.7 s after the edit (see how live testing works)
  • No terminal scrolling — results appear in your editor

Option 3: dotnet test (CI integration)

cd samples/from-koans/SageFs.Samples.Koans
dotnet test

All test projects include YoloDev.Expecto.TestSdk for dotnet test integration.

Using the .fsx Scripts

The original .fsx scripts are still available alongside the projects. They work as standalone SageFs exercises:

  1. Open any .fsx file in VS Code or Neovim
  2. Alt+Enter expressions to see results inline
  3. Fill in __ blanks to make tests pass
  4. Save — SageFs shows ✓/✗ gutter markers

The .fsx files have __ placeholders (the exercise). The .fs project files have solved answers (for verification).

Project Structure

All projects use:

  • The target framework inherited from Directory.Build.props (net11.0 as of 2026-10-01)
  • Central package management (versions in Directory.Packages.props)
  • Expecto with Expecto.Flip for testing
  • 2-space indentation (SageFs convention)