\prop_item:Nn vs \prop_get:NnN

[qinglee]

Currently, tabularray uses property lists to store some data. Also use \prop_item:Nn to get data from the list.

\prop_item:Nn is expandable and looks more natural and flexible. However, as the LaTeX3 documentation mentions, \prop_item:Nn is slower than the non-expandable analogue \prop_get:NnN. Expandability is not so important for tabularray. I'd rather use \prop_get:NnN for a little bit of performance.

[lvjr]

Yes, you are right. Most of the \prop_item:Nns can be replaced by \prop_get:NnNs in the package code.

At the beginning of the package, there are three similar functions \__tblr_prop_item (which calls \prop_item), \__tblr_spec_item and \__tblr_data_itemwhich correspond to three different data structures respectively. This make it easy to toggle among them and test which one provides the best performance.

If we are going to add \__tblr_prop_get which calls \prop_get, then we also need to add \__tblr_spec_get and \__tblr_data_get too.

PS: I'm sometimes confused because in some cases expandable macros are faster while in other cases non-expandable macros are faster.