=.l(on c(drain:cdr:read)(= l(map +(map[*(coerce(+""c)'num)_]`(1,@l))`(,@l 0))n
len.l))(pr:+"x^"n(map[+" "(if(< _ 0)'-'+)" "abs._(if(>(-- n)1)`(x^,n)(" x"n))]l))
Note that non-ascii characters in the above source code will be escaped (such as \x9f).