<p align="center">
<img src="icon.png" width="120" alt="Latch Logo" />
</p>
<h1 align="center">Latch</h1>
<p align="center">
<strong>Minimal scripting language for local automation and tool orchestration.</strong>
</p>
<p align="center">
<a href="https://crates.io/crates/latch-lang"><img src="https://img.shields.io/crates/v/latch-lang.svg" alt="crates.io" /></a>
<a href="https://github.com/kaelvalen/latch-lang/blob/main/LICENSE"><img src="https://img.shields.io/badge/license-MIT-blue.svg" alt="License: MIT" /></a>
</p>
---
Write `.lt` scripts to automate file operations, run shell commands, make HTTP calls, and orchestrate parallel tasks — all in a clean, readable syntax with zero boilerplate.
```python
# deploy.lt
branch := proc.exec("git branch --show-current").stdout
print("Deploying from ${branch}")
files := fs.glob("dist/**/*.js")
parallel f in files workers=4 {
proc.exec("aws s3 cp ${f} s3://my-bucket/${f}")
}
print("Deployed ${len(files)} files!")
stop 0
```
## Install
### From crates.io (recommended)
```sh
cargo install latch-lang
```
### From source
```sh
git clone https://github.com/kaelvalen/latch-lang.git
cd latch-lang
cargo install --path .
```
### Pre-built binaries
Download from [Releases](https://github.com/kaelvalen/latch-lang/releases) and add to your `PATH`.
After install, verify:
```sh
latch version
# → latch v0.1.0
```
## Quick Start
Create `hello.lt`:
```python
name := "World"
print("Hello, ${name}!")
items := ["files", "processes", "http", "parallel"]
for item in items {
print(" ✓ ${item}")
}
```
Run it:
```sh
latch run hello.lt
```
## Features
| **Variables** | `name := "latch"` |
| **Type annotations** | `port: int := 8080` |
| **String interpolation** | `"Hello ${name}!"` |
| **Lists & Maps** | `[1, 2, 3]`, `{"key": "val"}` |
| **Functions** | `fn greet(name) { return "hi ${name}" }` |
| **If / Else** | `if x > 0 { ... } else { ... }` |
| **For loops** | `for item in list { ... }` |
| **Parallel** | `parallel f in files workers=4 { ... }` |
| **Error handling** | `try { ... } catch e { ... }` |
| **Fallback values** | `data := fs.read("x") or "default"` |
| **Exit codes** | `stop 0` / `stop 1` |
| **File I/O** | `fs.read`, `fs.write`, `fs.exists`, `fs.glob` |
| **Shell commands** | `proc.exec("cmd")`, `proc.pipe([...])` |
| **HTTP** | `http.get(url)`, `http.post(url, body)` |
| **Time** | `time.now()`, `time.sleep(ms)` |
| **AI** | `ai.ask(prompt)`, `ai.summarize(text)` |
| **REPL** | `latch repl` |
## CLI
```sh
latch run <file.lt> # Run a script
latch check <file.lt> # Static analysis (no execution)
latch repl # Interactive REPL
latch version # Print version
```
## Standard Library
### Built-in Functions
```python
print("hello") # Print to stdout
len([1, 2, 3]) # → 3
str(42) # → "42"
int("7") # → 7
float("3.14") # → 3.14
typeof(x) # → "string"
push([1, 2], 3) # → [1, 2, 3]
keys({"a": 1}) # → ["a"]
values({"a": 1}) # → [1]
range(0, 5) # → [0, 1, 2, 3, 4]
split("a,b,c", ",") # → ["a", "b", "c"]
trim(" hi ") # → "hi"
contains("hello", "ell") # → true
replace("foo", "o", "0") # → "f00"
```
### Modules
```python
# fs — File System
content := fs.read("file.txt")
fs.write("out.txt", content)
fs.exists("path")
files := fs.glob("**/*.lt")
# proc — Processes
result := proc.exec("ls -la")
print(result.stdout)
result := proc.pipe(["cat log.txt", "grep ERROR", "wc -l"])
# http — HTTP Client
resp := http.get("https://api.example.com/data")
resp := http.post("https://api.example.com", "{\"key\": \"value\"}")
# Returns: {"body": "...", "status": 200}
# time — Time
now := time.now() # RFC 3339 timestamp
time.sleep(500) # Sleep 500ms
# ai — AI (requires LATCH_AI_KEY env var)
answer := ai.ask("Explain Rust in one sentence")
summary := ai.summarize(fs.read("article.txt"))
```
## Error Messages
Latch produces structured, actionable errors:
```
[latch] Semantic Error
file: deploy.lt
line: 12 col: 5
→ result := undeclared_var + 1
reason: Undefined variable 'undeclared_var'
hint: Declare the variable first with ':='
```
## Parallel Execution
Parallel blocks run all workers to completion. If any worker fails, the first error is returned after every worker has finished — no silent partial failures.
```python
servers := ["web-1", "web-2", "web-3", "web-4"]
parallel s in servers workers=4 {
proc.exec("ssh ${s} 'systemctl restart app'")
}
```
## Use as CI Exit Code
```python
result := proc.exec("cargo test")
if result.code != 0 {
print("Tests failed!")
stop 1
}
stop 0
```
## Examples
See the [examples/](examples/) directory:
- [`hello.lt`](examples/hello.lt) — Feature showcase
## Full Reference
See [docs/stdlib.md](docs/stdlib.md) for the complete standard library reference.
## License
MIT — see [LICENSE](LICENSE)
