Array subranges

A array variable may be explicitly coerced to a vector by specifying a subrange of bit indices. For example, the expression

        x[2..5]

is equivalent to

        [x[2],x[3],x[4],x[5]]

Similarly,

        x[5..2]

is equivalent to

        [x[5],x[4],x[3],x[2]]

Subranges may be used, for example, to extract bit fields, or to reverse the declared order bits in an array.