• y-or-n-p &optional control &rest arguments → generalized-boolean * yes-or-no-p{&optional control &rest arguments → generalized-boolean

control - a format control.

arguments - format arguments for control.

generalized-boolean - a generalized boolean.

These functions ask a question and parse a response from the user. They return true if the answer is affirmative, or false if the answer is negative.

y-or-n-p is for asking the user a question whose answer is either "yes" or "no." It is intended that the reply require the user to answer a yes-or-no question with a single character.

yes-or-no-p is also for asking the user a question whose answer is either "Yes" or "No." It is intended that the reply require the user to take more action than just a single keystroke, such as typing the full word yes or no followed by a newline.

y-or-n-p types out a message (if supplied), reads an answer in some implementation-dependent manner (intended to be short and simple, such as reading a single character such as Y or N). yes-or-no-p types out a message (if supplied), attracts the user's attention (for example, by ringing the terminal's bell), and reads an answer in some implementation-dependent manner (intended to be multiple characters, such as YES or NO).

If format-control is supplied and not nil, then a fresh-line operation is performed; then a message is printed as if format-control and arguments were given to format. In any case, yes-or-no-p and y-or-n-p will provide a prompt such as ""(Y or N) or ""(Yes or No) if appropriate.

All input and output are performed using query I/O.

(y-or-n-p "(t or nil) given by")

→

(t or nil) given by (Y or N) Y 

→

true 



(yes-or-no-p "a ~S message" 'frightening)

→

a FRIGHTENING message (Yes or No) no 

→

false 



(y-or-n-p "Produce listing file?")

▷

Produce listing file?
Please respond with Y or N. n 

→

false

Output to and input from query I/O will occur.

*query-io*.

None.

• Function FORMAT

yes-or-no-p and yes-or-no-p do not add question marks to the end of the prompt string, so any desired question mark or other punctuation should be explicitly included in the text query.

\issue{FORMAT-STRING-ARGUMENTS:SPECIFY}