Filter items from a list

(define-read-only (filter-item (l (list 100 uint)) (remove uint))
  (get newList (fold remove-value l { compareTo: remove, newList: (list) }))
)

(define-private (remove-value (listValue uint) (trackerTuple { compareTo: uint, newList: (list 100 uint) }))
  (merge trackerTuple {newList:
    (if (is-eq listValue (get compareTo trackerTuple))
      (get newList trackerTuple)
      (unwrap-panic (as-max-len? (append (get newList trackerTuple) listValue) u100))
    )
  })
)

;; Example usage
(filter-item (list u1 u2 u3 u2 u4) u2) ;; Returns (u1 u3 u4)

Use cases

Removing blacklisted addresses from access lists
Filtering out completed tasks from todo lists
Excluding specific tokens from portfolios
Data cleanup in smart contracts

Key concepts

This pattern uses fold to iterate through a list and build a new list:

Accumulator: Tracks the value to remove and builds the new list
Conditional append: Only adds items that don't match the filter
Type safety: Maintains list type and maximum length