Load .fss files, check their types, and run them inside your process. Your application decides which functions scripts can call.
dotnet tool install --global MagnusOpera.FScript
YOUR APPtype Customer =
{ Name: string
Plan: string
Seats: int }
[<export>] let quote (customer: Customer) =
let basePrice =
match customer.Plan with
| "scale" -> 29
| "team" -> 19
| _ -> 9
basePrice * customer.SeatsWhy embed a language?
Put changeable rules in .fss files. FScript checks them before execution, while your host keeps ownership of the database, network, filesystem, and other I/O.
What the code looks like
Functions, records, unions, and pattern matching. No class hierarchy required.
Use records and unions to describe the data a rule accepts and every result it can return.
type Decision =
| Approve of int
| Review of string
| Decline
let decide score =
match score with
| n when n > 80 -> Approve 5000
| n when n > 55 -> Review "manual"
| _ -> DeclineRegister typed host functions for the exact operations a script needs. Leave everything else out.
let notifyLateInvoice invoice =
match invoice.Status with
| "late" ->
Host.notify invoice.Owner
$"Invoice {invoice.Id} is late"
| _ ->
()Load a script, find its exported functions, and invoke them by name from .NET or JavaScript.
type Event = { Kind: string }
[<export>] let route (event: Event) =
match event.Kind with
| "signup" -> "onboarding"
| "payment.failed" -> "billing"
| "churn.risk" -> "success"
| _ -> "archive"The host sets the boundary
A script cannot query your database or send an HTTP request unless your host gives it a function that does so. Each extern has a name and a checked type signature.
Start with running code
The browser sandbox runs without an install. When the syntax makes sense, follow the host example for .NET or JavaScript.
Edit an FScript example and run it in the browser. Nothing to install.
Open sandbox 02Learn bindings, functions, data types, and pattern matching with working examples.
Take the tour 03Load a script, register externs, and call an exported function from your app.
Read the host example