Gren Compiler

0.6.5 verified Fri May 01 auth: no javascript

Compiler for the Gren programming language, a pure functional language designed for ease of learning and powerful use. Current stable version is 0.6.5, with an active release cadence. The compiler is split into a Gren frontend and a Haskell backend, with eventual goal of full self-hosting. Differentiators: zero-install package management, task ports, 'gren run' command, and a focus on simplicity.

Common errors

error error: Could not find module 'ModuleName' ↓

cause Module not in source files or dependencies.

fix

Ensure the module is exported and imported correctly. Check package.json or gren.json for dependencies.

error Type mismatch: expected X but got Y ↓

cause Function argument type mismatch.

fix

Correct the type of the argument or modify the function signature to match.

error error: 'gren install' is not a command. See 'gren --help'. ↓

cause Using old 'gren install' command.

fix

Use 'gren package install' instead.

error fatal: Could not read from stdin. (os error 5) ↓

cause Running 'gren run' without input redirection on some platforms.

fix

Provide input via file or pipe, or run interactively with terminal.

Warnings

breaking Version 0.5.0 replaced 'gren install' with 'gren package install'. Old syntax will fail. ↓

fix Use 'gren package install' instead of 'gren install'.

gotcha The compiler is split into two parts: a Gren frontend and a Haskell backend. Building from source requires both Node.js and Haskell dependencies. ↓

fix Use the official pre-built binary or follow build instructions with devbox.

deprecated Formatter command was removed in version 0.5.0. Using 'gren format' will error. ↓

fix Remove formatter usage; format manually or use an external tool.

gotcha The 'gren run' command requires the backend binary. If not found, it may fail silently. ↓

fix Set GREN_BIN environment variable to the backend executable path if needed.

gotcha Package manager rewritten in Gren in 0.6.0, enabling zero-install packages. However, old package caches may conflict. ↓

fix Delete old package cache at ~/.gren before upgrading.

Install

npm install gren-lang

yarn add gren-lang

pnpm add gren-lang

Imports

default

wrong

const Compiler = require('gren-lang')

correct

import Compiler from 'gren-lang'

Package is ESM-only; no CommonJS support.

compile

import { compile } from 'gren-lang/compiler'

Named export for compiling Gren source.

run
wrong
```
import { run } from 'gren-lang/run'
```
correct
```
import { run } from 'gren-lang'
```
The 'run' function is exported from the main package entry.

Quickstart

Compile and execute a Gren file, handling errors and outputting JavaScript.

import { compile, run } from 'gren-lang';
import { readFileSync, writeFileSync } from 'fs';

const source = readFileSync('hello.gren', 'utf8');
const result = compile(source, { optimize: false });
if (result.type === 'error') {
  console.error(result.errors);
  process.exit(1);
}
writeFileSync('output.js', result.code);
console.log('Compilation succeeded.');

// To run:
run('hello.gren', { args: [] });