ImplicitSpecies.n can be space and time dependent

[RemDelaporteMathurin]

Proposed changes

This fixes #644 by allowing the n attribute of ImplicitSpecies to be a function of x and t.

Pinging @kaelyndunnell

Usage:

density_func= lambda x: 10 - 10 * x[0]

empty = F.ImplicitSpecies(n=density_func, name="empty", others=[trapped_H])

Step function:

density_func= lambda x: ufl.conditional(ufl.gt(x[0], 0.5), 10, 0.0)

empty = F.ImplicitSpecies(n=density_func, name="empty", others=[trapped_H])

Types of changes

What types of changes does your code introduce to FESTIM?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• Black formatted
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.84%. Comparing base (8c5a965) to head (ad0ff2a).

Additional details and impacted files

@@             Coverage Diff             @@
##           fenicsx     #886      +/-   ##
===========================================
+ Coverage    97.80%   97.84%   +0.04%     
===========================================
  Files           44       44              
  Lines         2142     2182      +40     
===========================================
+ Hits          2095     2135      +40     
  Misses          47       47              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.