"""

```
writexyz(x::Vector{T}, file::String) where T <: AbstractVector
```

Print test xyz file.

"""
function writexyz(x::Vector{T}, file::String) where T <: AbstractVector
  f = open(file,"w")
  nx = length(x)
  println(f,nx)
  println(f,"title")
  for i in 1:nx
    println(f,"H $(x[i][1]) $(x[i][2]) $(x[i][3])")
  end
  close(f)
  nothing
end


