func sqrDiff(x1, x2 gotypes.Value) float64 {
result := 0.0
if x1.Type() == gotypes.Array {
a := x1.Array()
b := x1.Array()
for i := range a {
t := a[i].Real() - b[i].Real()
result += t * t
}
} else {
result = x1.Real() - x2.Real()
result *= result
}
return result
}
