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Grain (opens in a new tab) is a functional language targeting WASM. Its standard library uses WASI Preview 1.

First install grain from its official source:

brew install --no-quarantine --cask grain-lang/tap/grain

You also have to install everything as described in Common tooling.

The easiest way to get started once the tooling is installed is to use the golem new command as described in the Quickstart.

Otherwise you can start writing some code, the whole program will be exposed to Golem as a single parameterless run function:

let example1 = (a, b) => {
    a + b
print("Hello world!")
example1(100, 10)

First we have to compile the grain program to WASM:

grain compile --release main.gr

This results in a main.gr.wasm file which is a WASM module. We cannot write any WIT documents because there is no Grain binding generator available currently. This makes Grain a Tier 2 language, so we can convert the compiled module into a WASM component using the adapter from the tier2 directory of the golem package:

wasm-tools component new main.gr.wasm -o component.wasm --adapt tier2/wasi_snapshot_preview1.wasm
Make sure you use the tier2 adapter from the golem package!

The resulting component.wasm is ready to be used with Golem!