## Core

- Feature #1302: Simplify the way a Parameter is defined in the Lua input file: now there is only two fields: 'nature' and 'value', and the latter may understand a scalar value, a Lua function or an associative container that stands for 'piecewise_constant_by_domain'.
- Feature #1311: Same as #1302 for InitialCondition; however the 'piecewise_constant_by_domain' has not been implemented (it could easily but no use so far).

- Support #1314: Add in the interpretation of the Lua file a constraint upon the field Result.Display (namely forbids the value 0).
- Support #1304: Rename input_parameter_data input_data.

- Documentation #1312: Clarify in Lua option file the expected arguments of Lua functions in parameters and initial conditions.

- Bug #1310: Fix a bug concerning non enclosed parameter introduced in #1302.
- Bug #1301: In LuaOptionFile, fix the expected format given in the comment for associative containers

## Model instances

- Support #1306: In ModelInstance tests, use symlinks to the Lua file rather than copying them.

## Third party

- Support #1305 in standby: Apple Clang does not support yet std::variant, used in #1302 and #1311. I have therefore used for this platform boost::variant, and introduced macros to use either std::variant or boost::variant depending on the platform. However when std::variant is properly supported it will be cleaner to simply use std::variant everywhere.

## Backward incompatibility

In your own Models tu upgrade to v18.30 you will have to:

- Update the Lua files to use the new simplified interface for Parameters and InitialCondition (see #1302 and #1311).
- If you define your own Parameter in the input file, you will have to modify slightly the code to make it work. There are plenty of examples in Core library, for instance in Solid.VolumicMass.

I have already done this work for the public models in the Inria gitlab save from NonLinearOperator (which anyway needs some tickets resolved before moving forward...) and CardiacMechanics (a bit more work to update it).
This tag has no release notes.