Core library procedures and predicates depending on runtime data

[James_Feister]

What is `context.user_index` and `context.user_ptr` for?

They don’t do anything on their own, they’re just a place for you to put stuff when you don’t have a better way to do it. One of the most common cases it comes up in is as a means to pass userdata to a callback where you don’t have a dedicated argument to use to pass that data. For example, to sort some points by distance to some arbitrary point: points: [][3]f32 = ... target_pos: [3]f32 = ... context.user_ptr = &target_pos slice.sort_by(points[:], proc (a, b: [3]f32) -> bool { target_pos :…

context.user_ptr

May be what you are looking for.