Jisp is a project I (Rocketnia) made in a few days in March 2008, at a time when I was reading about Lisp and excited by how simple it looked to make my own implementation.
Some aspects of what I read about lisp dialects seemed needlessly inconsistent, such as the non-function-like behavior of quote and the non-quote-like syntax of string literals.
I'd been designing my own programming languages in paper notebooks for years before this point, and something as simple as Lisp seemed like a good place to start building and experimenting.
Unlike most Lisp dialects, Jisp has macros that take unparsed strings as input, rather than s-expressions. Here's an example, which you can test for yourself by running com.rocketnia.hacks.jisp.Jisp with a compiled version of the Proj/src/ directory in your Java classpath:
> (if (eq 'apple (cdr (cons 'pine 'apple))) 'success 'failure)
result: success
> something-we-havent-defined
result: ()
> (function-we-havent-defined 'symbol)
result: (() (quote symbol))
> "( this is a string )
result: "( this is a string )"
> (doublequote so is this )
result: "so is this"
> "and-this
result: "and-this"
> (if (eq 'string (doublequote string)) (exit) 'whoops)
result: whoops
> (if (eq "string (doublequote string)) (exit) 'whoops)
[The REPL terminates.]
Jisp has unified semantics for functions, special forms, macros, and string literals, making it easier to implement them all at once. The evaluation model similar to an fexpr-based Lisp dialect like Kernel, but I didn't know that at the time. Perhaps due to the string-based syntax, an even closer comparison would be Tcl.
My tinkering with Jisp came to an end shortly after I got through the initial challenge of writing the parser. The implementation of lambda is incomplete, and there are no meaningful I/O operations.
Rather than building upon the Jisp codebase, I rebuilt Jisp's style of Lisp-inspired but string-based syntax from scratch in later projects like Blade, Penknife Mk. I, and Chops (part of Lathe Comforts for JS).
To run Jisp, first install a distribution of the JDK. We've used Eclipse Temurin 17.0.1+12 from Adoptium, but Jisp should work even on much older JVM versions. (At the time of development in 2008, I was developing in Java 6 on the Sun Microsystems JDK.)
Then, run a build with the Gradle wrapper, and run the main class with an appropriate classpath:
./gradlew build
java -classpath lib/build/classes/java/main com.rocketnia.hacks.jisp.Jisp