Add hooks for constructing connections to and from modal representations

Add tests for some code generation bugs

Andreas Klöckner authored 3 years ago and Andreas Klöckner committed 3 years ago

Fix 'compiler' for the case that a subexpression occurs both in discr-cached and non-discr-cached code

The issue is that the same expression (dx0/dr0) appears in
both a user provided expression and the discretization
metrics and the code generator gets confused.

Co-authored-by: Andreas Klöckner <inform@tiker.net>

Fix 'compiler' for the case that a subexpression occurs both in discr-cached and non-discr-cached code