4.7.2 intvec expressions

An intvec expression is:

1. a range: int expression .. int expression
2. a repeated entry: int expression : positive int expression
   (a:b generates an intvec of length b>0 with identical entries a)
3. a function returning intvec
4. an expression involving intvec operations with int (+, -, *, /, %)
5. an expression of intvecs involving intvec operations (+, -)
6. an expression involving an intvec operation with intmat (*)
7. a type cast to intvec

Example: