Inspired by some The Expanse fanfiction, BELTABOL is an rpython-powered eager functional completely incomprehensible programming language, making it possible to write code such as:
Da gcd im fong max,walowda(wok)
wit wok(n,m) deting (chu
(n,m-n) detim n<m;
(n-m,m) detim n>m;
(n, m) detim owta).
or:
Da filter(p) im fong g
wit g(x) deting (chu
g(h):=:g(t) detim x?=h:=:t;
x detim x?=[i] && p(i);
x detim p(x);
unit(x) detim owta).
(in fact, the higher-order function walowda from the first example is written in BELTABOL itself, and provided in the standard prelude.)
For those who really must have it, a --boring flag to the interpreter allows the use of english keywords:
Print "aaaaaabaabaab".
Print calc expand("",eg)
where eg := [Lit("a"),Ptr(0,5),Lit("b"),Ptr(4,6)];
where expand(a,c) := (pick
expand(a++v , t) when c?=Lit(v) ++t;
expand(a , t) when c?=Ptr(s,0)++t;
expand(a++a@s,Ptr(s+1,n-1)++t) when c?=Ptr(s,n)++t;
a when otherwise);
where Comp ::= Lit(v) | Ptr(s,l).
The main idea is to play with rpython and rply; in fact the staged nature of rpython worked out very nicely, as one can use full python metagprogramming to aid with the grammar/ast interface (cf the parser source), while sticking with rpython for the (tree walking) interpreter results in ~50 times performance improvement compared to cpython.
Minimal documentation is available. While the language is expected to be extended, the semantics of the currently implemented fragment should stay reasonably constant.