The Turtle Programming Language ⓒ 2017

Turtle is copyrighted by Nigele McCoy. My goal was to make a very simple language with a paradigm shift.

Status

Turtle 0.9 is usable today: the full language, a standard library (data, linear algebra, SQL, HTTP, servers, JSON, files and more), a REPL, a formatter, a debugger, editor support, and turtle build for single-file programs on Mac, Windows and Linux.

Quick start

Install from a release (Mac .pkg, Windows setup, Linux .deb), or build it:

go build -o turtle ./cmd/turtle
./turtle path/to/script.turtle

On Windows (PowerShell):

go build -o turtle.exe ./cmd/turtle
.\turtle.exe path\to\script.turtle

See docs/getting-started.md for more.

A taste of Turtle

import time [now, sleep]
import mylib [binary]          // only what you list; mylib.turtle's variables stay private

def make_adder[n]              // functions are values; a nested def is a closure
    def adder[x]
        return x + n
    def [end]
    return adder
def [end]

add5 = make_adder[5]
show add5[1] .                 // 6

def log[msg]
    show msg .                 // no return, so the call yields none
def [end]

r = log["hi"]
show r == none .               // true

t = time now[]                 // naming the module always works, and is required
                               // when two imports both provide "now"

Working with data: give makes a quick function, and library functions read like sentences:

import data
import system [args, exists]

assemble Order [item, qty, price]    // your own type with named fields

orders = list [Order["pen", 3, 1.5], Order["pad", 1, 4.0], Order["mug", 5, 8.0]]
orders keep o give qty of o > 2 .   // a filter: keeps pen and mug

total = 0
[loop][o in orders]                  // for-each
    total = total + qty of o * price of o
[loop][end]
show total .                         // 44.5

names = list ["ana", "bo"]
names process n give n at upper .   // [ "ANA", "BO" ]
show names + list ["CY"] .           // [ "ANA", "BO", "CY" ]

[loop][path in args[]]               // turtle report.turtle notes.txt ...
    if ] path exists [
        show path, " found" .
    if [end]
[loop][end]

Full rules: docs/reference.md (Functions, Closures, Anonymous functions, Sentence-style calls, None, Assembled types, Loops, Modules) and the library docs (Data library, System library).

Documentation

• Getting started: build and run your first program
• Tour: the language, by example
• Reference: the complete syntax, with every keyword
• Library: one page per library (data, linear, sql, server, ...)
• REPL: the interactive prompt (turtle with no file)
• Testing: check, verify, validate, turtle test
• Editors: VS Code, Neovim, Helix and others
• Contributing and architecture: for working on Turtle itself
• Changelog

License

Turtle was created by Nigele McCoy, who holds its copyright. It is licensed under the Apache License 2.0; the license is what counts, but in short:

• Use it for anything, including commercial work.
• Change it and share it, keeping the LICENSE and NOTICE files.
• Programs you write in Turtle are yours.
• No warranty. Turtle is provided as is; its authors aren't liable for any damage or loss from using it (sections 7 and 8 of the license).
• Contributions are made under the same license, and what goes into official Turtle is the creator's decision.