Clearly state for each function in `Collections` to which data types it applies.

[chrillek]

Example: Apply is said to work on "Collections", which would include maps. It seems to be working with slices only, though. Then there's In, which is set to work on sets, with a set being a string, slice or array.
I suggest to clearly state in the definition of every function in the Collections set to which datatype(s) it can be applied or which datatype(s) it returns.

Aside: It might be confusing to introduce new terms like set in this context.

[jmooring]

Notes to self...

• Retain the current glossary entry for collection. It serves as an essential "umbrella" term covering slices (used in templates), maps, and arrays (used in serialized data¹).
• Unless there's a conflict in the content body, only change the front matter descriptions. See list.

Visit the function quick reference to see the new descriptions.

Footnotes

1. JSON/TOML/YAML/etc. have an array data type, not a slice data type. ↩