AoC 2021 day 5, part 2 (dc)

[q] SX

[1+] S1                             # inc
[_1*] SN                            # negate
[ d 0>N ] S|                        # abs
[ d l|x d 0=1 / ] SS                # sign

[ lc 1+ sc ] SC

[
    lp dd;g 1+ d 2=C r:g            # p -> (g(p)+1 = 2, count) g(p)+1 p p -> (g(p) = g(p)+1) p
    le=X                            # p -> (p = e, exit)
    lp ls+ sp                       # p -> (p = p+s)
    lIx
] SI

[
    z 0 =X                          # stop when stack empty
    sy sx sb sa                     # store top four in (x,y) and (a,b)

    ly 1000* lx+ sp                 # calculate pos
    lb 1000* la+ se                 # calculate end
    lb ly- lSx 1000* la lx- lSx+ ss # calculate step
    lIx

    [count = ]n lcps.

    lLx
] SL

0 sc                                # count = 0
lLx

[Part 2: ]n lcps.