INTP is a very small, minimal programming language. It's stack-based and similar to Forth, though actually heavily influenced by the more mathematically pure language Joy.
I wrote this in 2006 after discovering Joy, thinking it was really cool, and developing a yen to write a tiny programming language interpreter. Sadly I went a bit overboard by defining one-letter abbreviations for many C keywords, as you can see in abbr.h:
#define s static
#define i int
#define v void
#define r return
/* ... etc ... */The abbreviations helped keep my code small (just 12KB of C code) and made writing the interpreter fun because it felt like a different language, but of course they needlessly obfuscate the code. This is not a recommended way to write C!
Here is a short test program in INTP:
double
DUP CONCAT
%
main
"Hello" double double PRINT
%
As in Forth, routines in INTP are called “words”. This code defines two words, double and main. When the program is run, main runs. It pushes the string “Hello” onto the stack, calls double twice, and then prints the string on top of the stack to standard output. Each time double is called, it duplicates the thing on top of the stack, then pops the two strings at the top of the stack, concatenates them and pushes the result back onto the stack. In the end, this example prints “Hello” four times.
INTP has no explicit variables and everything operates directly on the stack. Pretty cool, huh? There's a wiki out there with a great overview of how concatenative languages work.
You can include another source file as a library by pushing its filename on the stack and calling the INCL word, e.g. "lib.intp" INCL. See substr.intp for an example using this.
As a language INTP is kind of cool but not original, because everything cool about it came from Joy. It's basically a second-rate Joy clone.