![]() ![]() If the Forth interpreter is going to execute the + word right now, it has to have the two numbers that are going to get added already on the stack. ![]() The corollary of this simple setup is that Forth uses the so-called Reverse Polish Notation (RPN). run this code! is valid Forth if you’ve already defined the words run, this, and code! and it calls each of the three words in the order that you’d expect. With a few exceptions for compiling, all words run right now so the Forth interpreter doesn’t have to look ahead to the next word. There’s no syntax, and all words are separated by a space and are parsed left to right. Forth is procedural in the extreme - a Forth program is really just a chain of subroutines, called “words” in the Forth jargon. Forth Crash Course: Theory Sectionįorth is the simplest language after assembly language. The hacker in me thinks that’s a lot of fun, and it’s a great match for smaller microcontroller projects. But if you want to tweak at the language itself, or use it to push your hardware around, or just play, Forth is fantastic. I’m not sure that it’s going to help you get “real work” done at all, and you engineer types might want to walk away now. Forth is a hacker’s language, in both the laudatory and the pejorative senses. On the other hand, a string of blinky LEDs running a physics simulation isn’t an “enterprise” anything. Faster Forths are implemented entirely in assembly language, with some compile-time optimizations that make it run about as fast as anything else, even though it’s compiled as you type, on the target microcontroller itself.įorth is probably not the language you want to learn if you are designing an enterprise banking backend. Some Forth implementations are written with just twenty or thirty functions in native assembly or C, and the rest is bootstrapped in Forth. You can modify the Forth compiler or interpreter itself, so if you want type checking, you can add it. If you like object-oriented style programming, for instance, Gforth comes with no fewer than three different object frameworks, and you get to choose whichever suits your problem or your style best. Almost nothing is included with most Forth systems by default. Forth is about simplicity and flexibility.īeing simple and flexible also means being extensible. If you want a compiler to worry about code safety for you, go see Rust, Ada, or Java. You will develop a good mental model of what data is on the stack at any given time, or you will suffer. (But why would you?) You can easily jump off into bad sections of memory and crash the system. You can do horrible things like redefine 2 as a function that will return seven, and forever after your math won’t work. There is no type checking, no scope, and no separation of data and code. It’s a fun language to write a hardware abstraction layer in.īut Forth is also like a high-wire act if C gives you enough rope to hang yourself, Forth is a flamethrower crawling with cobras. ![]() In my opinion, this combination of live coding and proximity to the hardware makes Forth great for exploring new microcontrollers or working them into your projects. You can, and must, peek and poke directly into memory in Forth, but you can also build up a body of higher-level code fast enough that you won’t mind. Is it a high-level language or a low-level language? Yes! Or rather, it’s the shortest path from one to the other. From Thinking FORTH (PDF)įorth is what you’d get if Python slept with Assembly Language: interactive, expressive, and without syntactical baggage, but still very close to the metal. When your Forth code is right, it reads just like a natural-language sentence but getting there involves a bit of puzzle solving. And all of this is simple enough that it’s easily capable of running in a few kilobytes of memory. Forth is a virtual machine, an interpreted command-line, and a compiler all in one. Coding in Forth is a little bit like writing assembly language, interactively, for a strange CPU architecture that doesn’t exist. Let’s start right off with a controversial claim: Forth is the hacker’s programming language.
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