2 ;;; An implementation of the Memory Array Redcode Simulator (MARS)
14 (define max-steps 10000)
20 (define ((make-instr opcode modifier A-mode A-num B-mode B-num name) . args)
22 (('copy n) (make-instr opcode modifier A-mode A-num B-mode B-num n))
24 (('modifier) modifier)
30 (('print) (print opcode
31 (if (null? modifier) "" (conc "." modifier))
32 " " (mode-string A-mode) A-num
33 ", " (mode-string B-mode) B-num
34 (if (null? name) "" (conc " ; " name))))
35 (('set-opcode! x n) (set! opcode x) (set! name n))
36 (('set-modifier! x n) (set! modifier x) (set! name n))
37 (('set-A-mode! x n) (set! A-mode x) (set! name n))
38 (('set-A-num! x n) (set! A-num x) (set! name n))
39 (('set-B-mode! x n) (set! B-mode x) (set! name n))
40 (('set-B-num! x n) (set! B-num x) (set! name n))))
42 (define (mode-string mode)
48 ((pre-indirect-A "{"))
49 ((pre-indirect-B "<"))
50 ((post-indirect-A "}"))
51 ((post-indirect-B ">"))))
53 (define initial-instruction
54 (make-instr 'DAT '() 'immediate 0 'immediate 0 '()))
57 ;;; Memory setup and addressing
60 (define core (make-vector core-size '()))
62 (define (initialize-core)
64 (unless (>= i core-size)
65 (vector-set! core i (initial-instruction 'copy '()))
70 (unless (>= i core-size)
71 ((vector-ref core i) 'print)
74 (define (addr+ . args)
76 (modulo (+ a b core-size) core-size))
82 (define (make-prog name instrs offset)
83 (list name instrs offset))
85 (define (prog-name prog) (list-ref prog 0))
86 (define (prog-instrs prog) (list-ref prog 1))
87 (define (prog-offset prog) (list-ref prog 2))
89 (define (install-prog prog addr)
91 (instrs (prog-instrs prog)))
92 (unless (null? instrs)
93 (vector-set! core ptr ((car instrs) 'copy (prog-name prog)))
94 (loop (addr+ ptr 1) (cdr instrs))))
95 (make-player (prog-name prog)
96 (addr+ addr (prog-offset prog))))
98 (define (can-install-prog? prog-len addr)
100 (remaining prog-len))
103 (if (null? ((vector-ref core ptr) 'name))
108 (define (install-progs progs)
109 (let loop ((players '())
111 (if (null? progs-left)
113 (let ((addr (pseudo-random-integer core-size))
114 (prog (car progs-left)))
115 (if (can-install-prog? (length (prog-instrs prog)) addr)
116 (loop (cons (install-prog prog addr) players)
118 (loop players progs-left))))))
120 (define (make-player name ptr)
123 (define (player-set-ptrs! player ptrs)
124 (set-cdr! prog-queue ptrs))
127 ;;; Executive function
130 (define (run players step)
132 ((> step max-steps) players) ;Tie between remaining players
133 ((<= (length players) 1) players) ;There's only one player left who thus wins
135 (let ((player (car players))
136 (other-players (cdr players))
137 (ptrs (player-ptrs player)))
138 (let ((new-ptrs (execute-instr (car ptrs))))
140 (run other-players (+ step 1))
142 (player-set-ptrs! (append (cdr ptrs) new-ptrs))
143 (run (append other-players (list player)) (+ step 1)))))))))
145 (define (execute-instr ptr)
146 (let* ((instr (vector-ref core ptr))
147 (A-pointer (eval-operand (instr-A-mode instr) (instr-A-num) ptr))
148 (B-pointer (eval-operand (instr-B-mode instr) (instr-B-num) ptr))
149 (modifier (instr-modifier instr)))
150 (case (instr-opcode instr)
151 ((DAT) '()) ;Game over, man, game over!
167 (error "Unrecognised opcode" (instr-opcode instr))))))
169 (define (eval-operand mode num ptr)
174 ((indirect-A) (addr+ num (instr-A-num (vector-ref core (addr+ ptr num)))))
175 ((indirect-B) (addr+ num (instr-B-num (vector-ref core (addr+ ptr num)))))
177 (let ((aux-instr (vector-ref core (addr+ ptr num))))
178 (instr-set-A-num! aux-instr (addr+ -1 (instr-A-num aux-instr)))
179 (addr+ num (instr-A-num aux-instr))))
181 (let ((aux-instr (vector-ref core (addr+ ptr num))))
182 (instr-set-B-num! aux-instr (addr+ -1 (instr-B-num aux-instr)))
183 (addr+ num (instr-B-num aux-instr))))
185 (let* ((aux-instr (vector-ref core (addr+ ptr num)))
186 (old-A-num (instr-A-num aux-instr)))
187 (instr-set-A-num! aux-instr (addr+ 1 (instr-A-num aux-instr)))
188 (addr+ num old-A-num)))
190 (let* ((aux-instr (vector-ref core (addr+ ptr num)))
191 (old-B-num (instr-B-num aux-instr)))
192 (instr-set-B-num! aux-instr (addr+ 1 (instr-B-num aux-instr)))
193 (addr+ num old-B-num)))
195 (error "Unrecognized mode" mode)))))