MIT Scheme

From MIT, for many systems, has comprehensive code library, includes most functionality of ANSI Standard Common Lisp (CLtL2), many low-level OS interactions. Distributed with system is LIAR (LIAR Imitates Apply Recursively), optimizing compiler that outputs native machine code, has Edwin interactive Emacs-derived editor written in pure Scheme and the subject of an MIT AI Lab Memo. Arguably one of the best Scheme systems available, unarguably one of largest. Major downfall: its not totally R5RS compliant, more so for hygienic macros and #f versus the empty list. Version 7.5 now available for x86 systems.