egison-5.0.0: lib/math/geometry/minkowski-space.egi

def coordinates {Num a} : Vector a := [t, x, y, z]

def metric {Num a} : Matrix a :=
  generateTensor
    (\match as list integer with
      | [#1, #1] -> -1
      | [$n, #n] -> 1
      | _        -> 0)
    [4, 4]