123 lines
3.2 KiB
Forth
123 lines
3.2 KiB
Forth
# https://adventofcode.com/2020/day/2
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#
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# To run (on Linux):
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# $ git clone https://github.com/akkartik/mu
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# $ cd mu
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# $ ./translate advent2020/2b.mu
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# $ ./a.elf < input
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#
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# You'll need to register to download the 'input' file for yourself.
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fn main -> _/ebx: int {
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var valid-password-count/edi: int <- copy 0
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var line-storage: (stream byte 0x100) # 256 bytes
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var line/edx: (addr stream byte) <- address line-storage
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var slice-storage: slice
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var slice/ecx: (addr slice) <- address slice-storage
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{
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# read line from stdin
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clear-stream line
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read-line-from-real-keyboard line
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# if line is empty (not even a newline), quit
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var done?/eax: boolean <- stream-empty? line
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compare done?, 0/false
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break-if-!=
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print-stream-to-real-screen line
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# slice = next-token(line, '-')
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next-token line, 0x2d, slice
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# pos1 = parse-int(slice)
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var _pos1/eax: int <- parse-decimal-int-from-slice slice
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var pos1/ebx: int <- copy _pos1
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var dash/eax: byte <- read-byte line # skip '-'
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# slice = next-token(line, ' ')
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next-token line, 0x20, slice
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var _pos2/eax: int <- parse-decimal-int-from-slice slice
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var pos2/esi: int <- copy _pos2
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print-int32-decimal 0, pos1
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print-string 0, " "
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print-int32-decimal 0, pos2
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print-string 0, "\n"
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compare pos1, pos2
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{
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break-if-<=
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print-string 0, "out of order!\n"
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return 1
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}
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# letter = next non-space
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skip-chars-matching-whitespace line
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var letter/eax: byte <- read-byte line
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# skip some stuff
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{
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var colon/eax: byte <- read-byte line # skip ':'
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}
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skip-chars-matching-whitespace line
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# now check the rest of the line
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var is-valid?/eax: boolean <- is-valid? pos1, pos2, letter, line
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compare is-valid?, 0/false
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{
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break-if-=
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print-string 0, "valid!\n"
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valid-password-count <- increment
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}
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loop
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}
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print-int32-decimal 0, valid-password-count
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print-string 0, "\n"
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return 0
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}
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# ideally password would be a random-access array
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# we'll just track an index
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# one benefit: we can easily start at 1
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fn is-valid? pos1: int, pos2: int, letter: byte, password: (addr stream byte) -> _/eax: boolean {
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var i/esi: int <- copy 1
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var letter-count/edi: int <- copy 0
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# while password stream isn't empty
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# c = read byte from password
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# if (c == letter)
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# if (i == pos1)
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# ++letter-count
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# if (i == pos2)
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# ++letter-count
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# ++i
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{
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#? print-string 0, " "
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#? print-int32-decimal 0, i
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#? print-string 0, "\n"
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var done?/eax: boolean <- stream-empty? password
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compare done?, 0/false
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break-if-!=
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var c/eax: byte <- read-byte password
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#? {
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#? var c2/eax: int <- copy c
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#? print-int32-decimal 0, c2
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#? print-string 0, "\n"
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#? }
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compare c, letter
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{
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break-if-!=
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compare i, pos1
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{
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break-if-!=
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letter-count <- increment
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#? print-string 0, " hit\n"
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}
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compare i, pos2
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{
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break-if-!=
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letter-count <- increment
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#? print-string 0, " hit\n"
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}
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}
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i <- increment
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loop
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}
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# return (letter-count == 1)
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compare letter-count, 1
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{
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break-if-!=
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return 1/true
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}
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return 0/false
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}
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