Portable, multi-language virtual machine and ANS Forth implementation for that virtual machine for desktops, mobile, embedded and scripting.
Sloth is a portable, multi-language, cross-platform Forth system.
It provides the minimal foundation needed to bootstrap ANS Forth and test it in any environment — desktop, mobile, or embedded.
It’s built on the idea that Forth itself — simple, extensible,
and close to the machine — should be available anywhere.
And not just across platforms, but also across languages.
That’s why Sloth is also designed to be embedded as a
scripting language within other applications.
ANS Forth also serves as a common virtual machine and high-level assembler, enabling the creation of higher-level languages that remain portable, lightweight, and consistent.
- Based on Forth: Utilizes Forth’s dual-stack, linear memory virtual machine for efficient computation from microcontrollers to large computers.
- Interactive programming: Designed for interactive use, allowing immediate feedback and iteration.
- Extensible: Easy to extend with additional backends and functionalities.
- Performance: Words can be implemented on the host for performance-critical sections without the need to modify sloth code.
- Embeddable: Can be used as a scripting language in other applications.
- Minimal native implementation: Most of the system is implemented in Forth itself, allowing easy porting to other platforms.
- Cross-language / cross-platform: Sloth aims to run on as many platforms and programming languages as possible. Right now there are a C implementation and a Java implementation.
- Easily hackable: Every part of Sloth should be simple enough for one developer to understand and modify for specific use cases.
Why the name Sloth?
Sloths are beautiful animals. And I liked the play on words:
“SLOw forTH.”
Later, I also thought of “Scripting Language Of The Hell/Heavens” —
and it stuck.
Why Forth?
These are interesting properties of some programming languages:
- Interactive like Lisp, Smalltalk, or Python
- Low-level enough for microcontrollers (like C)
- Simple enough to be implemented by a single developer
- No garbage collector for realtime applications
Forth is the only language that fulfills all four.
Continuous address space in all the implementations. C uses real native pointers and direct memory access. Java implementation uses memory "blocks" and addresses have two parts, one to index the block and another as the address inside the block.