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FScript

Your First Program

Create a file called hello.fs:

import Logger from 'std:logger'


greet = (name: String): String => 'hello ' + name


main = (): Undefined => {
  Logger.info(greet('FScript'))
}


main()

That program already shows a few core rules:

  • imports are explicit
  • functions use arrow syntax
  • the final expression in a block becomes the result
  • logging comes from std:logger, not a global console

Check it first

Terminal window
cargo run -p fscript-cli -- check hello.fs

If the file parses and typechecks, the CLI exits successfully.

Run it

Terminal window
cargo run -p fscript-cli -- run hello.fs

You should see the greeting printed through the current runtime-backed logger.

A slightly richer version

import Array from 'std:array'
import Logger from 'std:logger'


names = ['Ada', 'Grace', 'Linus']


messages = names
  |> Array.map((name) => 'hello ' + name)


main = (): Undefined => {
  Array.forEach((message) => Logger.info(message), messages)
}


main()

That example introduces pipes and explicit array helpers.

If you know JavaScript

A similar JavaScript example might use:

  • console.log
  • names.map(...)
  • function main() { return ... }

In FScript the same ideas become:

  • Logger.info
  • Array.map
  • arrow functions and final-expression blocks

Common early mistakes

  • forgetting to import the std: module you want to use
  • trying to call array prototype methods such as .map
  • writing return
  • trying to reassign a binding with let or const

Next step

Continue with Project Layout or jump into the Language Guide.