Function manipulating int8 values

gistfile1.jl

# Returns the new cell index from the specified cell in the
# specified direction.  The index is only valid if the
# starting cell and direction have been checked by the
# out_of_bounds function first.
function shift(cell_::Int8, dir::Int8)
    div5_mod2(x) = (x - 1)/5 % 2 != 0
    if dir == E
        return int8(cell_ + 1)
    elseif dir == ESE
        if div5_mod2(cell_)
            return int8(cell_ + 7)
        else
            return int8(cell_ + 6)
        end
    elseif dir == SE
        if div5_mod2(cell_)
            return int8(cell_ + 6)
        else
            return int8(cell_ + 5)
        end
    elseif dir == S
        return int8(cell_ + 10)
    elseif dir == SW
        if div5_mod2(cell_)
            return int8(cell_ + 5)
        else
            return int8(cell_ + 4)
        end
    elseif dir == WSW
        if div5_mod2(cell_)
            return int8(cell_ + 4)
        else
            return int8(cell_ + 3)
        end
    elseif dir == W
        return int8(cell_ - 1)
    elseif dir == WNW
        if div5_mod2(cell_)
            return int8(cell_ - 6)
        else
            return int8(cell_ - 7)
        end
    elseif dir == NW
        if div5_mod2(cell_)
            return int8(cell_ - 5)
        else
            return int8(cell_ - 6)
        end
    elseif dir == N
        return int8(cell_ - 10)
    elseif dir == NE
        if div5_mod2(cell_)
            return int8(cell_ - 4)
        else
            return int8(cell_ - 5)
        end
    elseif dir == ENE
        if div5_mod2(cell_)
            return int8(cell_ - 3) 
        else
            return int8(cell_ - 4)
        end
    end
    return cell_
end