chickadee » clojurian » doto

Inserts val as the first argument of each (proc args ...) clause (i.e. right after proc). Returns val. This is useful e.g. for mutating a record on initialization.

Example:

(define boolean-vector
  (doto (make-vector 100)
        (vector-fill! #t 0 50)
        (vector-fill! #f 50)))
=>

(define boolean-vector
  (let ((vec (make-vector 100)))
    (vector-fill! vec #t 0 50)
    (vector-fill! vec #f 50)
    vec))