AoC, day 5, edc

0k

# embedded perl to read line from stdin and push ASCII values of the characters
{ $_ = <>; chomp; return (map {ord} split //) } s?

[q] sQ                  # quit loop
[1+] s+                 # increment

0 s1                    # variable for storing result of part 1
[ ln s1 ] sS            # used for getting max, sets $1 to $n

#
# Macro to convert ASCII values on stack into seat number in $n
#
[
    z 0 =Q              # break if stack empty
    0r                  # put a zero under the top item to calculate bit on
    8% 4 >+             # using that the bit we want is not of bit 3 in ASCII
    ln 2*+ sn           # shift n and add bit to bottom
    lCx                 # loop
] sC

#
# Mainline
#
[
    l?x                 # grab input line as pushed ASCII values
    z 0 =Q              # quit if we don't get any more

    0 sn lCx            # init $n, then call C to calculate seat in it

    ln d                # push two copies of $n
    l1 <S               # first: get max of $n and $1
    1 r:a               # second: used set a[$n] = 1

    lMx                 # loop
] sM
lMx

[Part 1: ]n l1p

# Find seat for part 2 (assuming nice input where all seats contiguous but 1)
1- s2                   # take answer from part 1, decrement and store in $2
[
    l2 ;a 0 =Q          # break if a[$2] = 0 (empty seat)
    l2 1- s2            # decrement $2
    lIx                 # loop
] sI
lIx

[Part 2: ]n l2p