define DCALL[m,n]( a0?, ..., a(m-1)?, b0?, ..., b(n-1)?, c!, c(0,0)!, ..., c(m-1,n-1)! ) = pref *[ (a0? | ... | a(m-1)?); c! ] || pref *[ (a0? || b0?); d0! | ... | (a(i)? || b(j)?; d(i,j)! | ... | (a(m-1)? || b(n-1)?; d(m-1,n-1)! ] end