579 lines
No EOL
11 KiB
HTML
579 lines
No EOL
11 KiB
HTML
<!DOCTYPE HTML>
|
|
<HTML LANG="en-us"
|
|
><HEAD
|
|
><TITLE
|
|
>getf | Common Lisp Nova Spec</TITLE
|
|
><META CHARSET="US-ASCII"
|
|
><LINK REL="canonical" HREF="f_getf.html"
|
|
><LINK REL="next" HREF="f_remf.html" TYPE="text/html" TITLE="remf"
|
|
><LINK REL="prev" HREF="f_get-properties.html" TYPE="text/html" TITLE="get-properties"
|
|
><LINK REL="up" HREF="14_2_Conses_Dictionary.html" TYPE="text/html" TITLE="14.2 Conses Dictionary"
|
|
><LINK REL="start" HREF="index.html" TYPE="text/html" TITLE="Common Lisp Nova Spec"
|
|
><META NAME="VIEWPORT" CONTENT="width=device-width, initial-scale=1.0"
|
|
><LINK REL="STYLESHEET" HREF="dpans.css%3F3909942064.css"
|
|
><SCRIPT SRC="dpans.js%3F3909942064"
|
|
></SCRIPT
|
|
><SCRIPT SRC="apropos.js%3F3909942064"
|
|
></SCRIPT
|
|
></HEAD
|
|
><BODY
|
|
><DIV
|
|
><DIV CLASS="topnav"
|
|
><DIV CLASS="breadcrumb"
|
|
><SPAN CLASS="breadcrumb-item"
|
|
><A HREF="index.html"
|
|
>Common Lisp Nova Spec</A
|
|
></SPAN
|
|
> <SPAN CLASS="breadcrumb-item"
|
|
>→ <A HREF="14_Conses.html"
|
|
>14. Conses</A
|
|
></SPAN
|
|
> <SPAN CLASS="breadcrumb-item"
|
|
>→ <A HREF="14_2_Conses_Dictionary.html"
|
|
>14.2 Conses Dictionary</A
|
|
></SPAN
|
|
> <SPAN CLASS="breadcrumb-item"
|
|
>→ <A HREF="f_getf.html"
|
|
>getf</A
|
|
></SPAN
|
|
></DIV
|
|
><DIV CLASS="apropos"
|
|
><DIV CLASS="apropos-io"
|
|
><A HREF="f_get-properties.html" CLASS="prev"
|
|
>←</A
|
|
><SPAN ID="apropos-label"
|
|
>Apropos </SPAN
|
|
><INPUT ID="apropos" AUTOFOCUS="AUTOFOCUS" PLACEHOLDER="Type here to search" ONINPUT="aproposInput(this);" ONKEYUP="aproposKeyup(event);" ONCHANGE="aproposChange(this);" ONFOCUS="aproposFocus(this);" ONFOCUSOUT="aproposFocusout(this);"
|
|
><A HREF="f_remf.html" CLASS="next"
|
|
>→</A
|
|
></DIV
|
|
><DIV ID="apropos-res"
|
|
></DIV
|
|
></DIV
|
|
></DIV
|
|
><DIV CLASS="matter"
|
|
><DIV CLASS="com"
|
|
><DIV CLASS="begincom"
|
|
><HR
|
|
><TABLE WIDTH="100%" CELLSPACING="0" CELLPADDING="0"
|
|
><TR
|
|
><TD ALIGN="LEFT" VALIGN="BASELINE" WIDTH="100%" CLASS="name"
|
|
><SPAN CLASS="idx" DATA-KIND="idxref" DATA-TERM="getf"
|
|
></SPAN
|
|
><B
|
|
>getf</B
|
|
></TD
|
|
><TD ALIGN="RIGHT" VALIGN="BASELINE" WIDTH="0" NOWRAP="NOWRAP" CLASS="ftype"
|
|
><I
|
|
>Accessor</I
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><HR
|
|
></DIV
|
|
><UL CLASS="subtoc"
|
|
></UL
|
|
><DL
|
|
><DT
|
|
><B
|
|
>Syntax</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><B
|
|
>getf</B
|
|
> <SPAN CLASS="cmssi"
|
|
>plist</SPAN
|
|
> <SPAN CLASS="cmssi"
|
|
>indicator</SPAN
|
|
> <SPAN CLASS="cmtt"
|
|
>&optional</SPAN
|
|
> <SPAN CLASS="cmssi"
|
|
>default</SPAN
|
|
> <SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
> <SPAN CLASS="cmssi"
|
|
>value</SPAN
|
|
></P
|
|
><P CLASS="j"
|
|
><B
|
|
>(setf (getf</B
|
|
> <SPAN CLASS="cmssi"
|
|
>place</SPAN
|
|
> <SPAN CLASS="cmssi"
|
|
>indicator</SPAN
|
|
> <SPAN CLASS="cmtt"
|
|
>&optional</SPAN
|
|
> <SPAN CLASS="cmssi"
|
|
>default</SPAN
|
|
><B
|
|
>)</B
|
|
> <SPAN CLASS="cmssi"
|
|
>new-value</SPAN
|
|
><B
|
|
>)</B
|
|
></P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Arguments and Values</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>plist</VAR
|
|
> — a <A HREF="26_1_Glossary.html#property_list"
|
|
><EM CLASS="term"
|
|
>property list</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>place</VAR
|
|
> — a <A HREF="26_1_Glossary.html#place"
|
|
><EM CLASS="term"
|
|
>place</EM
|
|
></A
|
|
>, the <A HREF="26_1_Glossary.html#value"
|
|
><EM CLASS="term"
|
|
>value</EM
|
|
></A
|
|
> of which is a <A HREF="26_1_Glossary.html#property_list"
|
|
><EM CLASS="term"
|
|
>property list</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>indicator</VAR
|
|
> — an <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>default</VAR
|
|
> — an <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
>. The default is <SPAN CLASS="misc"
|
|
><B
|
|
>nil</B
|
|
></SPAN
|
|
>. </P
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>value</VAR
|
|
> — an <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
><VAR CLASS="param"
|
|
>new-value</VAR
|
|
> — an <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
>.</P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Description</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> finds a <A HREF="26_1_Glossary.html#property"
|
|
><EM CLASS="term"
|
|
>property</EM
|
|
></A
|
|
> on the <VAR CLASS="param"
|
|
>plist</VAR
|
|
> whose <A HREF="26_1_Glossary.html#property_indicator"
|
|
><EM CLASS="term"
|
|
>property indicator</EM
|
|
></A
|
|
> is <A HREF="26_1_Glossary.html#identical"
|
|
><EM CLASS="term"
|
|
>identical</EM
|
|
></A
|
|
> to <VAR CLASS="param"
|
|
>indicator</VAR
|
|
>, and returns its corresponding <A HREF="26_1_Glossary.html#property_value"
|
|
><EM CLASS="term"
|
|
>property value</EM
|
|
></A
|
|
>. If there are multiple <EM CLASS="term"
|
|
>properties</EM
|
|
><SPAN CLASS="meaning"
|
|
><SUB CLASS="sub"
|
|
><SPAN CLASS="cmr"
|
|
>1</SPAN
|
|
></SUB
|
|
></SPAN
|
|
> with that <A HREF="26_1_Glossary.html#property_indicator"
|
|
><EM CLASS="term"
|
|
>property indicator</EM
|
|
></A
|
|
>, <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> uses the first such <A HREF="26_1_Glossary.html#property"
|
|
><EM CLASS="term"
|
|
>property</EM
|
|
></A
|
|
>. If there is no <A HREF="26_1_Glossary.html#property"
|
|
><EM CLASS="term"
|
|
>property</EM
|
|
></A
|
|
> with that <A HREF="26_1_Glossary.html#property_indicator"
|
|
><EM CLASS="term"
|
|
>property indicator</EM
|
|
></A
|
|
>, <VAR CLASS="param"
|
|
>default</VAR
|
|
> is returned. </P
|
|
><P CLASS="j"
|
|
><A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
> of <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> may be used to associate a new <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
> with an existing indicator in the <A HREF="26_1_Glossary.html#property_list"
|
|
><EM CLASS="term"
|
|
>property list</EM
|
|
></A
|
|
> held by <VAR CLASS="param"
|
|
>place</VAR
|
|
>, or to create a new assocation if none exists. If there are multiple <EM CLASS="term"
|
|
>properties</EM
|
|
><SPAN CLASS="meaning"
|
|
><SUB CLASS="sub"
|
|
><SPAN CLASS="cmr"
|
|
>1</SPAN
|
|
></SUB
|
|
></SPAN
|
|
> with that <A HREF="26_1_Glossary.html#property_indicator"
|
|
><EM CLASS="term"
|
|
>property indicator</EM
|
|
></A
|
|
>, <A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
> of <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> associates the <VAR CLASS="param"
|
|
>new-value</VAR
|
|
> with the first such <A HREF="26_1_Glossary.html#property"
|
|
><EM CLASS="term"
|
|
>property</EM
|
|
></A
|
|
>. When a <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> <A HREF="26_1_Glossary.html#form"
|
|
><EM CLASS="term"
|
|
>form</EM
|
|
></A
|
|
> is used as a <A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
> <VAR CLASS="param"
|
|
>place</VAR
|
|
>, any <VAR CLASS="param"
|
|
>default</VAR
|
|
> which is supplied is evaluated according to normal left-to-right evaluation rules, but its <A HREF="26_1_Glossary.html#value"
|
|
><EM CLASS="term"
|
|
>value</EM
|
|
></A
|
|
> is ignored. </P
|
|
><P CLASS="j"
|
|
><A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
> of <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> is permitted to either <A HREF="26_1_Glossary.html#write"
|
|
><EM CLASS="term"
|
|
>write</EM
|
|
></A
|
|
> the <A HREF="26_1_Glossary.html#value"
|
|
><EM CLASS="term"
|
|
>value</EM
|
|
></A
|
|
> of <VAR CLASS="param"
|
|
>place</VAR
|
|
> itself, or modify of any part, <A HREF="26_1_Glossary.html#car"
|
|
><EM CLASS="term"
|
|
>car</EM
|
|
></A
|
|
> or <A HREF="26_1_Glossary.html#cdr"
|
|
><EM CLASS="term"
|
|
>cdr</EM
|
|
></A
|
|
>, of the <A HREF="26_1_Glossary.html#list_structure"
|
|
><EM CLASS="term"
|
|
>list structure</EM
|
|
></A
|
|
> held by <VAR CLASS="param"
|
|
>place</VAR
|
|
>.</P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Examples</B
|
|
></DT
|
|
><DD
|
|
><PRE CLASS="screen"
|
|
> (setq x '()) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> NIL
|
|
(getf x 'prop1) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> NIL
|
|
(getf x 'prop1 7) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> 7
|
|
(getf x 'prop1) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> NIL
|
|
(setf (getf x 'prop1) 'val1) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> VAL1
|
|
(eq (getf x 'prop1) 'val1) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> <A HREF="26_1_Glossary.html#true"
|
|
><EM CLASS="term"
|
|
>true</EM
|
|
></A
|
|
>
|
|
(getf x 'prop1) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> VAL1
|
|
(getf x 'prop1 7) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> VAL1
|
|
x <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (PROP1 VAL1)
|
|
|
|
;; Examples of implementation variation permitted.
|
|
(setq foo (list 'a 'b 'c 'd 'e 'f)) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (A B C D E F)
|
|
(setq bar (cddr foo)) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (C D E F)
|
|
(remf foo 'c) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> <A HREF="26_1_Glossary.html#true"
|
|
><EM CLASS="term"
|
|
>true</EM
|
|
></A
|
|
>
|
|
foo <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (A B E F)
|
|
bar
|
|
<SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (C D E F)
|
|
<SPAN CLASS="sp"
|
|
><SPAN CLASS="arrow withabove"
|
|
><SPAN CLASS="above"
|
|
>or </SPAN
|
|
>→</SPAN
|
|
></SPAN
|
|
> (C)
|
|
<SPAN CLASS="sp"
|
|
><SPAN CLASS="arrow withabove"
|
|
><SPAN CLASS="above"
|
|
>or </SPAN
|
|
>→</SPAN
|
|
></SPAN
|
|
> (NIL)
|
|
<SPAN CLASS="sp"
|
|
><SPAN CLASS="arrow withabove"
|
|
><SPAN CLASS="above"
|
|
>or </SPAN
|
|
>→</SPAN
|
|
></SPAN
|
|
> (C NIL)
|
|
<SPAN CLASS="sp"
|
|
><SPAN CLASS="arrow withabove"
|
|
><SPAN CLASS="above"
|
|
>or </SPAN
|
|
>→</SPAN
|
|
></SPAN
|
|
> (C D)</PRE
|
|
></DD
|
|
><DT
|
|
><B
|
|
>See Also</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_get.html" CLASS="funref"
|
|
><B
|
|
>get</B
|
|
></A
|
|
>, <A HREF="f_get-properties.html" CLASS="funref"
|
|
><B
|
|
>get-properties</B
|
|
></A
|
|
>, <A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
>, <A HREF="5_1_Generalized_Reference.html#sec_5_1_2_2" CLASS="secref"
|
|
><SPAN CLASS="cmr"
|
|
>Section</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>5.1.2.2</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>(Function</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Call</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Forms</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>as</SPAN
|
|
> <SPAN CLASS="cmr"
|
|
>Places)</SPAN
|
|
></A
|
|
></P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Notes</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
>There is no way (using <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
>) to distinguish an absent property from one whose value is <VAR CLASS="param"
|
|
>default</VAR
|
|
>; but see <A HREF="f_get-properties.html" CLASS="funref"
|
|
><B
|
|
>get-properties</B
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>Note that while supplying a <EM CLASS="term"
|
|
>default</EM
|
|
> argument to <A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
> in a <A HREF="f_setf.html" CLASS="macref"
|
|
><B
|
|
>setf</B
|
|
></A
|
|
> situation is sometimes not very interesting, it is still important because some macros, such as <A HREF="f_push.html" CLASS="macref"
|
|
><B
|
|
>push</B
|
|
></A
|
|
> and <A HREF="f_incf.html" CLASS="macref"
|
|
><B
|
|
>incf</B
|
|
></A
|
|
>, require a <VAR CLASS="param"
|
|
>place</VAR
|
|
> argument which data is both <A HREF="26_1_Glossary.html#read"
|
|
><EM CLASS="term"
|
|
>read</EM
|
|
></A
|
|
> from and <EM CLASS="term"
|
|
>written</EM
|
|
> to. In such a context, if a <EM CLASS="term"
|
|
>default</EM
|
|
> argument is to be supplied for the <A HREF="26_1_Glossary.html#read"
|
|
><EM CLASS="term"
|
|
>read</EM
|
|
></A
|
|
> situation, it must be syntactically valid for the <A HREF="26_1_Glossary.html#write"
|
|
><EM CLASS="term"
|
|
>write</EM
|
|
></A
|
|
> situation as well. For example,</P
|
|
><PRE CLASS="screen"
|
|
>(let ((plist '()))
|
|
(incf (getf plist 'count 0))
|
|
plist) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (COUNT 1)</PRE
|
|
></DD
|
|
></DL
|
|
></DIV
|
|
></DIV
|
|
><DIV CLASS="footer"
|
|
><DIV CLASS="btmnav"
|
|
><A HREF="f_get-properties.html" CLASS="prev"
|
|
>←</A
|
|
><A HREF="f_remf.html" CLASS="next"
|
|
>→</A
|
|
></DIV
|
|
><DIV CLASS="trail"
|
|
>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
|
|
></DIV
|
|
></DIV
|
|
><SCRIPT
|
|
>domReady();</SCRIPT
|
|
></BODY
|
|
></HTML
|
|
> |