Express constraints on specific values in a list

[bmaclach]

Currently in Drasil, constraints can either be expressed as a Range, EnumeratedReal, or EnumeratedStr.

Another type of constraint we need to express are constraints on specific elements of a list. An example in SSP is that the first and last elements of the list x_wt must be the same as the first and last elements of the list x_slope.

This might be more an issue of adding to Expr a way to access an element of a vector. It also requires being able to express constraints on equality, but related issue #1795 covers that.

[JacquesCarette]

You are correct that the right way to do this first involves fixing #1795 and then to change Expr to do indexing properly.

[JacquesCarette]

So that last part probably is best done by me - and thus the correct assignees.