Using the Haskell Host SDK
Check your installation
Please be sure you've installed Extism before continuing with this guide.
1. Install the Haskell library
Add the dependency to your cabal file:
library
build-depends: extism
2. Import the library and use the APIs
Count Vowels Plugin
code.wasm
in this example is our example plugin that counts vowels. If you want to run this, download it first and set the path:
curl https://raw.githubusercontent.com/extism/extism/main/wasm/code.wasm > code.wasm
Main.hs
module Main where
import Extism
import Extism.Manifest(manifest, wasmFile)
unwrap (Right x) = x
unwrap (Left (ErrorMessage msg)) = do
error msg
main = do
-- NOTE: if you encounter an error such as:
-- "Unable to load plugin: unknown import: wasi_snapshot_preview1::fd_write has not been defined"
-- change `False` to `True` in the following function to provide WASI imports to your plugin.
plugin <- unwrap <$> Extism.createPluginFromManifest (manifest [wasmFile "../wasm/code.wasm"]) False
res <- unwrap <$> Extism.call plugin "count_vowels" (Extism.toByteString "this is a test")
putStrLn (Extism.fromByteString res)
Extism.free plugin
Need help?
If you've encountered a bug or think something is missing, please open an issue on the Extism GitHub repository.
There is an active community on Discord where the project maintainers and users can help you. Come hang out!