a(1)[2]{3}
a(1){2}[3]
a[1](2){3}
a[1]{2}(3)
a{1}(2)[3]
a{1}[2](3)


ℤ[]

ℤ[:]
ℤ[head:]
ℤ[:tail]
ℤ[head:tail]

ℤ[::]
ℤ[ : : ]
ℤ[head::]
ℤ[head: :]
ℤ[:tail:]
ℤ[::step]
ℤ[: :step]
ℤ[head:tail:]
ℤ[:tail:step]
ℤ[head::step]
ℤ[head: :step]
ℤ[head:tail:step]