The development of Algol played an important role in establishing
computer science as an academic discipline. The Algol 68 Genie
project preserves Algol 68 out of educational as well as
scientific-historical interest, by making available Algol 68 Genie;
a recent, well-featured implementation written from scratch. Algol
68 Genie is a practically full implementation of the language
defined by the Revised Report. The implementation is a hybrid
compiler-interpreter; units with considerable interpreter-overhead
can optionally be compiled.

Note: 'a68g --compile' requires <quadmath.h> from gcc 8+.

Homepage:
https://algol68genie.nl/en/algol-68-genie/
