CopySubset
An animation that copies a subset of the from variable to the into variable. Type information is always lost in the copy (even if you select the entirey of the from variable). However, do note that the from variables are not modified at all during this process (as it is a copy. Also, to make semantics clear, we required that the into variable be in line with its follower (that is, there cannot be any changes to the into variable since its last Set). This is easy to fix by simply calling Set: on the into variable right before this animation if you need to.
| from& | The sources of the animation. Note that from can be a variable tree |
| tag_predicate(tag) | This specifies the subset of the from variable that should be transferred over to the target into variabl |
| into& | The destination of the animation. Note that into CANNOT be a variable tree, it must be a single variable |
An animation the executes the copy. The from iterators and followers are all unaffected, whereas the into iterators and followers are going to be iterator original content + the transferred content
func CopySubset([subset] {[main] {from&, tag_predicate(tag)}}, into&)