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I want to define a struct for chores

(defstruct chore name sector assignments)

where the assignments slot is a vector with seven positions. I know that the above syntax will generate the getters chore-name, chore-sector and chore-assignments. But I would like to have something like this (chore-assignment 1 c). Is there any syntax that will give me this “for free” or should I code the function myself?

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Yes and no. No, because chore-assignment doesn't let you modify what's inside the value of the assignment slot; it only lets you modify the assignment slot itself.

Instead, Lisp has setf, which has some really good tricks up its sleeves. The first argument to setf is a PLACE, which is any expression which can be interpreted as a place to store a value. Often this is just a variable name, but it can be much more complex. Just based on your question, I think you've already been using something like this:

(setf (chore-assignments c) (vector foo bar baz))

You can also do more:

(setf (aref (chore-assignments c) 1) 42)

Note that the PLACE in this assignment is not the whole assignments vector, it's one individual element inside the vector, exactly as you wanted.

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