AoC 2024 day 17, part 1 (dc)

# Command: perl -00 -pe 's/\D*(\d+),?/$1 /g' <input | dc -fdc-p1.dc | sed -e's/,$//'

# Load registers
? sc sb sa
?   # blank line

# Load code
? zsn
[
    z1-:c
    z0<L
] dsLx

# XOR of top two elements (lowest three bits)
# Uses (A + B*(-1^A)) % 4 for 2-bits and +2% for the third
[
    4~ 3R 4~                # (B-low2) (B-rest) (A-low2) (A-rest)
    3R
    d_1r^3R*+4d3R+r%        # (B^A low2) (B-rest) (A-rest)
    _3R
    +2%                     # (B^A third) (B^A low2)
    4*+
] s^

[ s.laq ] sA    # replace top with A
[ s.lbq ] sB    # replace top with B
[ s.lcq ] sC    # replace top with C

# Resolve combo referencing:
[
    d 4=A
    d 5=B
    d 6=C
] sR

[r] sr

[ lRx 2r^ lar/ sa ] 0:o     # adv
[ lRx 2r^ lar/ sb ] 6:o     # bdv
[ lRx 2r^ lar/ sc ] 7:o     # cdv

[ lRx 8% sb ]       2:o     # bst
[ lRx 8% n44an ]    5:o     # out

[ 2- la 0!=r s. ]   3:o     # jnz

[ lb l^x sb ]       1:o     # bxl
[ s. lblc l^x sb ]  4:o     # bxc

# stack frame: ip
0
[
    dd 1+;c
    r;c ;ox                 # [block]x arg ip => ip
    2+d ln>M
] dsMx