99 lines
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99 lines
4.2 KiB
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<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Section 6.1.8.1</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="06_ah.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="06_ah.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="06_ai.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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6.1.8.1 Examples of clause grouping</H2>
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<PRE>
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;; Group conditional clauses.
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(loop for i in '(1 324 2345 323 2 4 235 252)
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when (oddp i)
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do (print i)
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and collect i into odd-numbers
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and do (terpri)
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else ; I is even.
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collect i into even-numbers
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finally
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(return (values odd-numbers even-numbers)))
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>> 1
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>>
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>> 2345
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>>
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>> 323
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>>
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>> 235
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=> (1 2345 323 235), (324 2 4 252)
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;; Collect numbers larger than 3.
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(loop for i in '(1 2 3 4 5 6)
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when (and (> i 3) i)
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collect it) ; IT refers to (and (> i 3) i).
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=> (4 5 6)
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;; Find a number in a list.
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(loop for i in '(1 2 3 4 5 6)
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when (and (> i 3) i)
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return it)
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=> 4
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;; The above example is similar to the following one.
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(loop for i in '(1 2 3 4 5 6)
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thereis (and (> i 3) i))
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=> 4
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;; Nest conditional clauses.
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(let ((list '(0 3.0 apple 4 5 9.8 orange banana)))
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(loop for i in list
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when (numberp i)
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when (floatp i)
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collect i into float-numbers
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else ; Not (floatp i)
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collect i into other-numbers
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else ; Not (numberp i)
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when (symbolp i)
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collect i into symbol-list
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else ; Not (symbolp i)
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do (error "found a funny value in list ~S, value ~S~%" list i)
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finally (return (values float-numbers other-numbers symbol-list))))
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=> (3.0 9.8), (0 4 5), (APPLE ORANGE BANANA)
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;; Without the END preposition, the last AND would apply to the
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;; inner IF rather than the outer one.
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(loop for x from 0 to 3
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do (print x)
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if (zerop (mod x 2))
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do (princ " a")
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and if (zerop (floor x 2))
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do (princ " b")
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end
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and do (princ " c"))
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>> 0 a b c
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>> 1
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>> 2 a c
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>> 3
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=> NIL
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</PRE>
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</TT> <P>
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