Function `substring-` functions are not implemented in Metapath processor

[aj-stein-gsa]

User Story

As a developer of Metaschema-based software, in order to write more efficient and easier to read Metapath in my models, I would like this library to implement the function substring-after().

Goals

• [ ] Implement the substring class of functions for Metapath use:
  • [ ] fn:substring: #142
  • [ ] fn:substring-before
  • [ ] fn:substring-after
• [ ] Provide positive correct use of the function in unit tests
• [ ] Provide incorrect correct negative use of the function unit tests

Dependencies

N/A

Acceptance Criteria

• [ ] All website and readme documentation affected by the changes in this issue have been updated.
• [x] A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• [ ] The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

Revisions

No response

[david-waltermire]

Would it make sense to implement the following all at once?

• [ ] fn:substring
• [ ] fn:substring-before
• [ ] fn:substring-after

I'd suggest skipping the collation variants of these functions. There is no support for collations yet and this would be a significant lift.

[aj-stein-gsa]

Sure I just wanted to do it this weekend or early next week to keep myself sharp. Adjust the issue?