3 element list specification of &optional or &key argument

(defun do-it (previous-balance additional-funds

&optional (report nil print-title))

(let ((new-balance (+ previous-balance additional-funds)))

(when print-title

(if report

(print "Issuing report")

(print "Not issuing report"))

(when report

(format t "~%current balance is ~,2f" new-balance)))

new-balance))

CL-USER(14): (do-it 50 10)

60

CL-USER(15): (do-it 50 10 t)

"Issuing report"

current balance is 60.00

60

CL-USER(16): (do-it 50 10 nil)

"Not issuing report"

60

CL-USER(17):

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