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99 Bottles of Beer/Lisp: Difference between revisions
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See [[99 Bottles of Beer/Lisp]]
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=={{header|Common Lisp}}==
===Sensible solution===
<lang lisp>(defun bottles (x)
(loop for bottles from x downto 1
do (format t "~a bottle~:p of beer on the wall
~:*~a bottle~:p of beer
Take one down, pass it around
~a bottle~:p of beer on the wall~2%" bottles (1- bottles))))</lang>
and then just call
<lang lisp>(bottles 99)</lang>
===Ridiculous===
<lang lisp>(format t "~{~[~^~]~:*~D bottle~:P of beer on the wall~%~:*~D bottle~:P of beer~%Take one down, pass it around~%~D bottle~:P~:* of beer on the wall~2%~}"
(loop :for n :from 99 :downto 0 :collect n))</lang>
The [http://www.lispworks.com/documentation/HyperSpec/Body/22_c.htm FORMAT function] is probably the most baroque (i.e. featureful almost to a fault) function in Common Lisp. To really drive this point home, try replacing each instance of <tt>~D</tt> with <tt>~R</tt>, and then with <tt>~@R</tt>. Yes, this is all standard and dependable (dys?)functionality.
Explanation of the format string for the uninitiated:
* <tt>~{<i>fmt</i>~}</tt> expects the next argument to be a list (which is of the integers from 99 down to 0), and executes the format string <i>fmt</i> on each element. It is essentially a map or foreach.
* <tt>~[...~]</tt> is a case/switch. It executes the <i>n</i>th clause, where <i>n</i> is taken from the next argument. Since there is only one clause here, it will be executed only when the argument is 0.
* <tt>~^</tt> will terminate formatting.
* <tt>~:*</tt> will back-up to the most-recently used argument.
* <tt>~D</tt> prints the next argument as a decimal number.
* <tt>~:P</tt> is for English plurals: it prints <tt>s</tt> if the last argument wasn't 1; it prints nothing otherwise. There's also <tt>~@P</tt> for <tt>y</tt>/<tt>ies</tt>, in case you were worried about that.
Note, by the way, how the emoticons <tt>:*~D</tt> and <tt>:P</tt> have shown up in the format string. FORMAT is so powerful, it's even self-aware about how silly it is.
=={{header|PicoLisp}}==
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