317 lines
7 KiB
HTML
317 lines
7 KiB
HTML
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>loop-finish | Common Lisp Nova Spec</TITLE
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>→ <A HREF="f_loop-finish.html"
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>loop-finish</A
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><DIV CLASS="matter"
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><TABLE WIDTH="100%" CELLSPACING="0" CELLPADDING="0"
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><TR
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><TD ALIGN="LEFT" VALIGN="BASELINE" WIDTH="100%" CLASS="name"
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><SPAN CLASS="idx" DATA-KIND="idxref" DATA-TERM="loop-finish"
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></SPAN
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><B
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>loop-finish</B
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></TD
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><TD ALIGN="RIGHT" VALIGN="BASELINE" WIDTH="0" NOWRAP="NOWRAP" CLASS="ftype"
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><I
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>Local</I
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> <I
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>Macro</I
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></TD
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></TR
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></TABLE
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><HR
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></DIV
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><UL CLASS="subtoc"
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></UL
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><DL
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><DT
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><B
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>Syntax</B
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></DT
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><DD
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><P CLASS="j"
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><B
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>loop-finish</B
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> ⟨<I
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>no</I
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> <A HREF="26_1_Glossary.html#argument"
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><EM CLASS="term"
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>arguments</EM
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></A
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>⟩ <SPAN CLASS="arrow"
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>→</SPAN
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>|</P
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></DD
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><DT
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><B
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>Description</B
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></DT
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><DD
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><P CLASS="j"
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>The <A HREF="f_loop-finish.html" CLASS="macref"
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><B
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>loop-finish</B
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></A
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> <A HREF="26_1_Glossary.html#macro"
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><EM CLASS="term"
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>macro</EM
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></A
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> can be used lexically within an extended <A HREF="f_loop.html" CLASS="macref"
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><B
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>loop</B
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></A
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> <A HREF="26_1_Glossary.html#form"
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><EM CLASS="term"
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>form</EM
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></A
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> to terminate that <A HREF="26_1_Glossary.html#form"
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><EM CLASS="term"
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>form</EM
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></A
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> “normally.” That is, it transfers control to the loop epilogue of the lexically innermost extended <A HREF="f_loop.html" CLASS="macref"
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><B
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>loop</B
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></A
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> <A HREF="26_1_Glossary.html#form"
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><EM CLASS="term"
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>form</EM
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></A
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>. This permits execution of any <SPAN CLASS="macref"
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><B
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>finally</B
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></SPAN
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> clause (for effect) and the return of any accumulated result.</P
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></DD
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><DT
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><B
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>Examples</B
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></DT
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><DD
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><PRE CLASS="screen"
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>;; Terminate the loop, but return the accumulated count.
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(loop for i in '(1 2 3 stop-here 4 5 6)
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when (symbolp i) do (loop-finish)
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count i)
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 3
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;; The preceding loop is equivalent to:
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(loop for i in '(1 2 3 stop-here 4 5 6)
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until (symbolp i)
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count i)
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> 3
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;; While LOOP-FINISH can be used can be used in a variety of
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;; situations it is really most needed in a situation where a need
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;; to exit is detected at other than the loop's `top level'
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;; (where UNTIL or WHEN often work just as well), or where some
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;; computation must occur between the point where a need to exit is
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;; detected and the point where the exit actually occurs. For example:
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(defun tokenize-sentence (string)
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(macrolet ((add-word (wvar svar)
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`(when ,wvar
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(push (coerce (nreverse ,wvar) 'string) ,svar)
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(setq ,wvar nil))))
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(loop with word = '() and sentence = '() and endpos = nil
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for i below (length string)
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do (let ((char (aref string i)))
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(case char
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(#\Space (add-word word sentence))
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(#\. (setq endpos (1+ i)) (loop-finish))
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(otherwise (push char word))))
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finally (add-word word sentence)
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(return (values (nreverse sentence) endpos)))))
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> TOKENIZE-SENTENCE
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(tokenize-sentence "this is a sentence. this is another sentence.")
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> ("this" "is" "a" "sentence"), 19
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(tokenize-sentence "this is a sentence")
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<SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> ("this" "is" "a" "sentence"), NIL</PRE
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></DD
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><DT
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><B
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>Side Effects</B
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></DT
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><DD
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><P CLASS="j"
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>Transfers control.</P
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></DD
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><DT
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><B
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>Exceptional Situations</B
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></DT
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><DD
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><P CLASS="j"
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>Whether or not <A HREF="f_loop-finish.html" CLASS="macref"
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><B
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>loop-finish</B
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></A
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> is <A HREF="26_1_Glossary.html#fbound"
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><EM CLASS="term"
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>fbound</EM
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></A
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> in the <A HREF="26_1_Glossary.html#global_environment"
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><EM CLASS="term"
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>global environment</EM
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></A
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> is <A HREF="26_1_Glossary.html#implementation-dependent"
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><EM CLASS="term"
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>implementation-dependent</EM
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></A
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>; however, the restrictions on redefinition and <A HREF="26_1_Glossary.html#shadow"
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><EM CLASS="term"
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>shadowing</EM
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></A
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> of <A HREF="f_loop-finish.html" CLASS="macref"
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><B
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>loop-finish</B
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></A
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> are the same as for <A HREF="26_1_Glossary.html#symbol"
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><EM CLASS="term"
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>symbols</EM
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></A
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> in the <SPAN CLASS="packref"
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><SPAN CLASS="cmtt"
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>COMMON-LISP</SPAN
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></SPAN
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> <A HREF="26_1_Glossary.html#package"
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><EM CLASS="term"
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>package</EM
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></A
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> which are <A HREF="26_1_Glossary.html#fbound"
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><EM CLASS="term"
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>fbound</EM
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></A
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> in the <A HREF="26_1_Glossary.html#global_environment"
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><EM CLASS="term"
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>global environment</EM
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></A
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>. The consequences of attempting to use <A HREF="f_loop-finish.html" CLASS="macref"
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><B
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>loop-finish</B
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></A
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> outside of <A HREF="f_loop.html" CLASS="macref"
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><B
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>loop</B
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></A
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> are undefined.</P
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></DD
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><DT
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><B
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>See Also</B
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></DT
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><DD
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><P CLASS="j"
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><A HREF="f_loop.html" CLASS="macref"
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><B
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>loop</B
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></A
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>, <A HREF="6_1_The_LOOP_Facility.html#sec_6_1" CLASS="secref"
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><SPAN CLASS="cmr"
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>Section</SPAN
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> <SPAN CLASS="cmr"
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>6.1</SPAN
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> <SPAN CLASS="cmr"
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>(The</SPAN
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> <SPAN CLASS="cmr"
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>LOOP</SPAN
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> <SPAN CLASS="cmr"
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>Facility)</SPAN
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></A
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></P
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></DD
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><DT
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><B
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>Notes</B
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></DT
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></DL
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><A HREF="f_loop.html" CLASS="prev"
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>←</A
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><DIV CLASS="trail"
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>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
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