Forth language! Implemented as a Racket #lang.
From the package server:
> raco pkg install forth
From source:
> git clone https://github.com/bennn/forth
> raco pkg install ./forth
All files starting with #lang forth are interpreted as a sequence of Forth commands.
#lang forth
push 2 ;; add `2` to the stack
push 2
+ ;; add the top two numbers on the stack
dup ;; duplicate head of stack
2 ;; short for `push 2`
swap ;; swap order of top 2 stack arguments
-
: incr 1 + ;; define a new command `incr`
incr
incr
+
To open an interactive session, run raco forth.
Running raco pkg install forth installs forth as a Racket package.
Since the package contains a directory named lang/ that contains a file reader.rkt, the new package can be used as a #lang.
Racket uses to reader defined in reader.rkt to process programs that begin with #lang forth.
(Official docs here)
All reader.rkt modules need to provide the functions read and read-syntax.
These functions must produce a Racket module (docs here).
In this project, read just calls read-syntax, which reads all lines from the file and interprets them as forth commands.
The interpreting happens during compilation and produces a stack.
After evaluating all commands in the module, our read-syntax function returns a module; inside the module, we save the stack to a variable.
Doing so makes the stack available inside the Dr. Racket interactions panel.
One more thing: this package's info.rkt file defines the raco forth command.
Docs here.)