91 lines
4.0 KiB
Racket
91 lines
4.0 KiB
Racket
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#lang racket
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(require racket/vector
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"../lib.rkt")
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(provide string->program
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exec)
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(define (vector-ref** vec pos)
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(vector-ref* vec pos 0))
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;; string->program : string -> (listof number)
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;; A program is a list of numbers,
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;; which are sequences of instructions and parameters.
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(define (string->program str)
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(list->vector (map string->number (string-split str ","))))
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;; exec* : program -> number -> number -> (listof number) -> (listof number) -> program
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;; An encoded instruction is anywhere from 1 to 4 digits long.
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;; The last one or two digits represent the opcode, which can be:
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;; - 1/2: add/multiply parameters 1 and 2 and store in parameter 3
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;; - 3: take an input and store in parameter 1
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;; - 4: output parameter 1
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;; - 5/6: if parameter 1 is non-zero/zero, jump to parameter 2
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;; - 7/8: if parameter 1 is less-than/equal-to parameter 2,
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;; store 1 else store 0 in parameter 3
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;; - 9: add parameter 1 to relative base
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;; - 99: halt
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;; The next few digits to the left of the opcode (if any) represent
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;; the mode of each parameter, with that of parameter i in the digit
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;; i digits to the left of the opcode.
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;; If the mode is 0, the value at pointer is an address.
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;; If the mode is 1, the value at pointer is immediate.
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;; If the mode is 2, the value at pointer is an address to be offset by base.
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;; Note that leading zeroes in the encoded instruction are omitted.
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(define (exec* program #:ptr [pointer 0] #:base [base 0] #:in [input '()] #:out [output '()])
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(define instruction (vector-ref** program pointer))
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(define opcode (remainder instruction 100))
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(define next-pointer
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(match opcode
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[(or 1 2 7 8) (+ pointer 4)]
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[(or 3 4 9) (+ pointer 2)]
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[(or 5 6) (+ pointer 3)]
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[99 (+ pointer 1)]))
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(define (get-location index mode)
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(match mode
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[0 (vector-ref** program (+ pointer index))]
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[1 (+ pointer index)]
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[2 (+ (vector-ref** program (+ pointer index)) base)]))
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(let* ([mode1 (remainder (quotient instruction 100) 10)]
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[mode2 (remainder (quotient instruction 1000) 10)]
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[mode3 (remainder (quotient instruction 10000) 10)]
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;; l* : call to get write location from program
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[l1 (λ () (get-location 1 mode1))]
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[l2 (λ () (get-location 2 mode2))]
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[l3 (λ () (get-location 3 mode3))]
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;; v* : call to read values from program
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[v1 (λ () (vector-ref** program (l1)))]
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[v2 (λ () (vector-ref** program (l2)))]
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[v3 (λ () (vector-ref** program (l3)))])
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(match opcode
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[(or 1 2)
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(let* ([arith (match opcode [1 +] [2 *])]
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[value (arith (v1) (v2))]
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[program (vector-set!* program (l3) value)])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[3
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(let* ([value (car input)]
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[input (cdr input)]
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[program (vector-set!* program (l1) value)])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[4
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(let* ([output (append output `(,(v1)))])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[(or 5 6)
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(let* ([jump-if (match opcode [5 nzero?] [6 zero?])]
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[next-pointer (if (jump-if (v1)) (v2) next-pointer)])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[(or 7 8)
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(let* ([lt-eq (match opcode [7 <] [8 =])]
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[value (if (lt-eq (v1) (v2)) 1 0)]
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[program (vector-set!* program (l3) value)])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[9
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(let ([base (+ base (v1))])
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(exec* program #:ptr next-pointer #:base base #:in input #:out output))]
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[99 (values program output)])))
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;; Just so we always run the program on a fresh copy
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(define (exec program #:ptr [pointer 0] #:base [base 0] #:in [input '()] #:out [output '()])
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(exec* (vector-copy program) #:ptr pointer #:base base #:in input #:out output))
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