// add.tm   add unary strings of zeros
// input tape  000...00 000..00  blank separated, blank at end
// output tape  000...000  sum of zeros on input tape
// #b used as a blank, ## epsilon, empty string, do not write

start s0
halt  s9 // use halt rather than 'final' when computing a result
limit 20
trace all

s0 0  s0 ## R   skip over initial 0's
s0 #b s1 0  R   write 0 over blank
s1 0  s1 ## R   keep moving
s1 #b s2 ## L   detect at end
s2 0  s9 #b R   blank extra 0

enddef
// test cases
tape 000#b00#b   should end with five zeros on tape

tape 00#b0000#b