1 # Advent of code 2017, problem 1a
 2 #   https://adventofcode.com/2017/day/1
 3 #
 4 # Mu solution by Sumeet Agarwal and Kartik Agaram
 5 #   https://archive.org/details/2021-06-02-akkartik-sumeet
 6 #
 7 # To build on Linux:
 8 #   $ git clone https://github.com/akkartik/mu
 9 #   $ cd mu/linux
10 #   $ ./translate apps/advent2017/1a.mu            # emits a.elf
11 # To run on Linux:
12 #   Download https://adventofcode.com/2017/day/1/input
13 #   $ ./a.elf < input
14 # Type in the number returned at https://adventofcode.com/2017/day/1
15 
16 fn main -> _/ebx: int {
17   var input_stream: (stream byte 0x8000)
18   var input_stream_addr/esi: (addr stream byte) <- address input_stream
19 
20   var sum/edi: int <- copy 0
21   read-line-from-real-keyboard input_stream_addr
22 
23   var temp/eax: int <- read_digit input_stream_addr
24   var first_digit/ebx: int <- copy temp
25   var this_digit/edx: int <- copy temp
26 
27   {
28     var done?/eax: boolean <- stream-empty? input_stream_addr
29     compare done?, 1
30     break-if-=
31 
32     var next_digit/eax: int <- read_digit input_stream_addr
33     # hacky newline check
34     compare next_digit, 0
35     break-if-<
36 
37     {
38       compare this_digit, next_digit
39       break-if-!=
40       sum <- add this_digit
41     }
42 
43     this_digit <- copy next_digit
44 
45     loop
46   }
47 
48   # the last iteration will need to compare the last number to the first
49   {
50     compare this_digit, first_digit
51     break-if-!=
52     sum <- add this_digit
53   }
54 
55   print-int32-decimal 0, sum
56 
57   return 0/ok
58 }
59 
60 fn read_digit input_stream_addr: (addr stream byte) -> _/eax: int {
61   var next_digit/eax: byte <- read-byte input_stream_addr
62   next_digit <- subtract 0x30
63   var next_digit/eax: int <- copy next_digit
64   return next_digit
65 }