An antonym for peel would be to unpeel, to put the skin back on. I am not looking for that, but rather, for something that extracts and retains whatever is valuable or central or essential or edible from something -- what would be left after you peels something, or what you get by removing the center of something with a spoon. (Is there a word for words that are in this kind of opposition, I wonder?)
"Pith" and "core," as verbs, both come close to what I am looking for, but in common usage both suggest that it is that object that has been cored or pithed that we value, want, and intend to keep. I am hoping for a word that is like "core," but suggests that it is the core we intend to keep. I want to set up an opposition between two actions, peel and "X," the first of which removes a small valuable piece or layer from a useless bulk, contrasted to removing an essential or valuable core or mass from a useless coating or after discarding a valueless dross.
My goal is to find a pair of words to serve as a mnemonic for a more abstract pair of actions that applies to certain data structures, as in:
The peel() function extracts the listed elements from the data structure, while the "X"() function returns a full copy of the data structure after discarding the listed elements.
I spent some time paging through a couple of thesauruses looking at antonyms for peel and synonyms for core or pith, all three as verbs, and did not find anything useful.
The problem of both "peel" and "core," for my purposes, is that the usual implication for what you value in performing the actions is backwards. I want an alternative or pair of alternative that says when I peel something, I do it because I want the peel (and am discarding the core), and when I core something, I do it because I want the core (and am discarding the peel).
This question analogizes my data structures to fruit or the like, but I am open to entirely different metaphors so long as they set up the opposition between two actions, one removing and keeping a small valuable piece from a valueless bulk, and the other keeping a valuable bulk while discarding valueless elements.