Next steps in S4

[kamapu]

Next steps in S4

[kamapu]

S4 implemented in 2f8304c

[kamapu]

Sequence for HTML and other displays:

• view_html() for S3 and S4 classes.
• search_repo() for both classes including view_html().
• view_pdf() perhaps also implemented in search_repo(). Consider use of yamlme as dependency.

[kamapu]

Following internals:

• gr2text() for S3 and S4
• rmd_templates() for HTML (Shiny) and PDF.
• clean() for S4 class (table data_sets optional) and subset() (alternative for three main tables) for S4 class.