"var"/"seq" for/while
=====================

Require "var" (or perhaps "seq") keyword on for/while when the same object
(e.g. array element or variable) may be read and written (or only written)
in different iterations?

This would allow for implicit parallelization, as well as vectorizations,
in the default case.

For implicit parallelization and vectorization to be used in the right
situations, we need to know if the number of iterations is large or small.
Perhaps there could be some attribute on arrays and length/count variables
that indicate the approximate size?