Day 4: 424, Christmas tree (sort of)

d4golf.hs

@@ -6,9 +6,13 @@ w p=head.rights.p
 a?b|c a,i b=b|let=l 0
 k d i|i==l d=r d|let=i
 (x:y)#f=m(x!)(a x f):y#a x f
-v[]=[];v s=tail(take 6 s):v(drop 6 s)
-s(v:t)|'.'>v=[]:s t|(x:u)<-s t=(v:x):u
-p(x:y)=m read(s x)#v(m(m(l.read).words)y)
-m=map;r=pure;l=Left;c=isLeft;z=zipWith;i=isRight
+a&x|(u,_:v)<-break(==x)a=u:v&x|let=[a]
+p(x:(_:y))=m read(x&',')#(m(m(l.read).words)y&[])
 x!d|h d||h(foldr(z(:))e d)=r$(x*)$sum$lefts=<<d|let=l 0
 main=interact$show.((,).w((\(b,h:_)->z(?)(last b)h).span(any c))<*>w(filter i=<<)).p.lines
+m=map
+r=pure
+l=Left
+c=isLeft
+z=zipWith
+i=isRight