528 lines
No EOL
10 KiB
HTML
528 lines
No EOL
10 KiB
HTML
<!DOCTYPE HTML>
|
|
<HTML LANG="en-us"
|
|
><HEAD
|
|
><TITLE
|
|
>get | Common Lisp Nova Spec</TITLE
|
|
><META CHARSET="US-ASCII"
|
|
><LINK REL="canonical" HREF="f_get.html"
|
|
><LINK REL="next" HREF="f_remprop.html" TYPE="text/html" TITLE="remprop"
|
|
><LINK REL="prev" HREF="f_symbol-value.html" TYPE="text/html" TITLE="symbol-value"
|
|
><LINK REL="up" HREF="10_2_Symbols_Dictionary.html" TYPE="text/html" TITLE="10.2 Symbols 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="10_Symbols.html"
|
|
>10. Symbols</A
|
|
></SPAN
|
|
> <SPAN CLASS="breadcrumb-item"
|
|
>→ <A HREF="10_2_Symbols_Dictionary.html"
|
|
>10.2 Symbols Dictionary</A
|
|
></SPAN
|
|
> <SPAN CLASS="breadcrumb-item"
|
|
>→ <A HREF="f_get.html"
|
|
>get</A
|
|
></SPAN
|
|
></DIV
|
|
><DIV CLASS="apropos"
|
|
><DIV CLASS="apropos-io"
|
|
><A HREF="f_symbol-value.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_remprop.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="get"
|
|
></SPAN
|
|
><B
|
|
>get</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
|
|
>get</B
|
|
> <SPAN CLASS="cmssi"
|
|
>symbol</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 (get</B
|
|
> <SPAN CLASS="cmssi"
|
|
>symbol</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"
|
|
>symbol</VAR
|
|
> — a <A HREF="26_1_Glossary.html#symbol"
|
|
><EM CLASS="term"
|
|
>symbol</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
|
|
> — if the indicated property exists, the <A HREF="26_1_Glossary.html#object"
|
|
><EM CLASS="term"
|
|
>object</EM
|
|
></A
|
|
> that is its <A HREF="26_1_Glossary.html#value"
|
|
><EM CLASS="term"
|
|
>value</EM
|
|
></A
|
|
>; otherwise, the specified <VAR CLASS="param"
|
|
>default</VAR
|
|
>. </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_get.html" CLASS="funref"
|
|
><B
|
|
>get</B
|
|
></A
|
|
> finds a <A HREF="26_1_Glossary.html#property"
|
|
><EM CLASS="term"
|
|
>property</EM
|
|
></A
|
|
> on the <A HREF="26_1_Glossary.html#property_list"
|
|
><EM CLASS="term"
|
|
>property list</EM
|
|
></A
|
|
><SPAN CLASS="meaning"
|
|
><SUB CLASS="sub"
|
|
><SPAN CLASS="cmr"
|
|
>2</SPAN
|
|
></SUB
|
|
></SPAN
|
|
> of <VAR CLASS="param"
|
|
>symbol</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_get.html" CLASS="funref"
|
|
><B
|
|
>get</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_get.html" CLASS="funref"
|
|
><B
|
|
>get</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 already on the <VAR CLASS="param"
|
|
>symbol</VAR
|
|
>’s <A HREF="26_1_Glossary.html#property_list"
|
|
><EM CLASS="term"
|
|
>property list</EM
|
|
></A
|
|
>, 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_get.html" CLASS="funref"
|
|
><B
|
|
>get</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_get.html" CLASS="funref"
|
|
><B
|
|
>get</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
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Examples</B
|
|
></DT
|
|
><DD
|
|
><PRE CLASS="screen"
|
|
> (defun make-person (first-name last-name)
|
|
(let ((person (gensym "PERSON")))
|
|
(setf (get person 'first-name) first-name)
|
|
(setf (get person 'last-name) last-name)
|
|
person)) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> MAKE-PERSON
|
|
(defvar *john* (make-person "John" "Dow")) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> *JOHN*
|
|
*john* <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> #:PERSON4603
|
|
(defvar *sally* (make-person "Sally" "Jones")) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> *SALLY*
|
|
(get *john* 'first-name) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> "John"
|
|
(get *sally* 'last-name) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> "Jones"
|
|
(defun marry (man woman married-name)
|
|
(setf (get man 'wife) woman)
|
|
(setf (get woman 'husband) man)
|
|
(setf (get man 'last-name) married-name)
|
|
(setf (get woman 'last-name) married-name)
|
|
married-name) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> MARRY
|
|
(marry *john* *sally* "Dow-Jones") <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> "Dow-Jones"
|
|
(get *john* 'last-name) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> "Dow-Jones"
|
|
(get (get *john* 'wife) 'first-name) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> "Sally"
|
|
(symbol-plist *john*)
|
|
<SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> (WIFE #:PERSON4604 LAST-NAME "Dow-Jones" FIRST-NAME "John")
|
|
(defmacro age (person &optional (default ''thirty-something))
|
|
`(get ,person 'age ,default)) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> AGE
|
|
(age *john*) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> THIRTY-SOMETHING
|
|
(age *john* 20) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> 20
|
|
(setf (age *john*) 25) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> 25
|
|
(age *john*) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> 25
|
|
(age *john* 20) <SPAN CLASS="cmsy"
|
|
><SPAN CLASS="arrow"
|
|
>→</SPAN
|
|
></SPAN
|
|
> 25</PRE
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Exceptional Situations</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
>Should signal an error of <A HREF="26_1_Glossary.html#type"
|
|
><EM CLASS="term"
|
|
>type</EM
|
|
></A
|
|
> <A HREF="t_type-error.html" CLASS="typeref"
|
|
><B
|
|
>type-error</B
|
|
></A
|
|
> if <VAR CLASS="param"
|
|
>symbol</VAR
|
|
> is not a <A HREF="26_1_Glossary.html#symbol"
|
|
><EM CLASS="term"
|
|
>symbol</EM
|
|
></A
|
|
>.</P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>See Also</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_getf.html" CLASS="funref"
|
|
><B
|
|
>getf</B
|
|
></A
|
|
>, <A HREF="f_symbol-plist.html" CLASS="funref"
|
|
><B
|
|
>symbol-plist</B
|
|
></A
|
|
>, <A HREF="f_remprop.html" CLASS="funref"
|
|
><B
|
|
>remprop</B
|
|
></A
|
|
></P
|
|
></DD
|
|
><DT
|
|
><B
|
|
>Notes</B
|
|
></DT
|
|
><DD
|
|
><PRE CLASS="screen"
|
|
>(get x y) <SPAN CLASS="cmsy"
|
|
><SPAN STYLE="font-size:16px;vertical-align:-2px"
|
|
>≡</SPAN
|
|
></SPAN
|
|
> (getf (symbol-plist x) y)</PRE
|
|
><P CLASS="j"
|
|
><A HREF="26_1_Glossary.html#number"
|
|
><EM CLASS="term"
|
|
>Numbers</EM
|
|
></A
|
|
> and <A HREF="26_1_Glossary.html#character"
|
|
><EM CLASS="term"
|
|
>characters</EM
|
|
></A
|
|
> are not recommended for use as <VAR CLASS="param"
|
|
>indicators</VAR
|
|
> in portable code since <A HREF="f_get.html" CLASS="funref"
|
|
><B
|
|
>get</B
|
|
></A
|
|
> tests with <A HREF="f_eq.html" CLASS="funref"
|
|
><B
|
|
>eq</B
|
|
></A
|
|
> rather than <A HREF="f_eql.html" CLASS="funref"
|
|
><B
|
|
>eql</B
|
|
></A
|
|
>, and consequently the effect of using such <VAR CLASS="param"
|
|
>indicators</VAR
|
|
> is <A HREF="26_1_Glossary.html#implementation-dependent"
|
|
><EM CLASS="term"
|
|
>implementation-dependent</EM
|
|
></A
|
|
>. </P
|
|
><P CLASS="j"
|
|
>There is no way using <A HREF="f_get.html" CLASS="funref"
|
|
><B
|
|
>get</B
|
|
></A
|
|
> to distinguish an absent property from one whose value is <VAR CLASS="param"
|
|
>default</VAR
|
|
>. However, see <A HREF="f_get-properties.html" CLASS="funref"
|
|
><B
|
|
>get-properties</B
|
|
></A
|
|
>.</P
|
|
></DD
|
|
></DL
|
|
></DIV
|
|
></DIV
|
|
><DIV CLASS="footer"
|
|
><DIV CLASS="btmnav"
|
|
><A HREF="f_symbol-value.html" CLASS="prev"
|
|
>←</A
|
|
><A HREF="f_remprop.html" CLASS="next"
|
|
>→</A
|
|
></DIV
|
|
><DIV CLASS="trail"
|
|
>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
|
|
></DIV
|
|
></DIV
|
|
><SCRIPT
|
|
>domReady();</SCRIPT
|
|
></BODY
|
|
></HTML
|
|
> |