Trac: Allow indirect variable lookups

[MichaelClerx]

https://chaste.cs.ox.ac.uk/trac/ticket/2019

That is, lookup a name which evaluates to a string, then lookup the variable with that name. This would allow protocols to be parameterised on the name of a parameter to scan over, for instance.

Should mainly need some additions to Environment::Lookup method, with an extra parameter (default true) saying whether to allow indirection (calls to delegatees would pass false). Also some handling in AssignmentStatement and other places which can set variables.

[MichaelClerx]

Not sure I understand this one

[jonc125]

It's a new language feature proposal. Would add strings as a fundamental datatype (alongside numbers), let you have vectors of strings (useful for plot keys), and let you do the equivalent of Python's getattr. Probably not needed if we start allowing arbitrary Python for post-processing though!