MixFix Parsing - An idea

[mattulbrich]

This PR is meant as a wip - tryout - branch for mixfix parsing in KeY

Related Issue

We want to define syntax for symbols in .key files.
This here allows you to do so.

Intended Change

You can now do this:

\functions {
   int myExp(int, int) \syntax _/30 !! _/30;
   int mySeqGet(Seq, int) \syntax _/100 --> _ <--;
   int myadd(int, int) \syntax _/40 ++ _/40;
}

\problem {
  ~ 3 ++ 3 !! 4 ++ (seqEmpty --> 3 <--) ~ > 0
}

In this experiment branch you need to add ~ to enter mixfix parsing.

Type of pull request

• Bug fix (non-breaking change which fixes an issue)
• Refactoring (behaviour should not change or only minimally change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• There are changes to the (Java) code
• There are changes to the taclet rule base
• There are changes to the deployment/CI infrastructure (gradle, github, ...)
• Other:

Ensuring quality

It is still WIP.

• I made sure that introduced/changed code is well documented (javadoc and inline comments).
• I made sure that new/changed end-user features are well documented (https://github.com/KeYProject/key-docs).
• I added new test case(s) for new functionality.
• I have tested the feature as follows: ...
• I have checked that runtime performance has not deteriorated.

The contributions within this pull request are licensed under GPLv2 (only) for inclusion in KeY.

[wadoon]

• ANTLR side is working.
• Current test subject is de.uka.ilkd.key.nparser.ExprTest
• Missing rules for integer & co.