393 lines
7.2 KiB
HTML
393 lines
7.2 KiB
HTML
|
<!DOCTYPE HTML>
|
||
|
|
<HTML LANG="en-us"
|
||
|
|
><HEAD
|
||
|
|
><TITLE
|
||
|
|
>symbol-value | Common Lisp Nova Spec</TITLE
|
||
|
|
><META CHARSET="US-ASCII"
|
||
|
|
><LINK REL="canonical" HREF="f_symbol-value.html"
|
||
|
|
><LINK REL="next" HREF="f_get.html" TYPE="text/html" TITLE="get"
|
||
|
|
><LINK REL="prev" HREF="f_symbol-plist.html" TYPE="text/html" TITLE="symbol-plist"
|
||
|
|
><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_symbol-value.html"
|
||
|
|
>symbol-value</A
|
||
|
|
></SPAN
|
||
|
|
></DIV
|
||
|
|
><DIV CLASS="apropos"
|
||
|
|
><DIV CLASS="apropos-io"
|
||
|
|
><A HREF="f_symbol-plist.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_get.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="symbol-value"
|
||
|
|
></SPAN
|
||
|
|
><B
|
||
|
|
>symbol-value</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
|
||
|
|
>symbol-value</B
|
||
|
|
> <SPAN CLASS="cmssi"
|
||
|
|
>symbol</SPAN
|
||
|
|
> <SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
> <SPAN CLASS="cmssi"
|
||
|
|
>value</SPAN
|
||
|
|
></P
|
||
|
|
><P CLASS="j"
|
||
|
|
><B
|
||
|
|
>(setf (symbol-value</B
|
||
|
|
> <SPAN CLASS="cmssi"
|
||
|
|
>symbol</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
|
||
|
|
> that must have a <A HREF="26_1_Glossary.html#value"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>value</EM
|
||
|
|
></A
|
||
|
|
>. </P
|
||
|
|
><P CLASS="j"
|
||
|
|
><VAR CLASS="param"
|
||
|
|
>value</VAR
|
||
|
|
>, <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="26_1_Glossary.html#access"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>Accesses</EM
|
||
|
|
></A
|
||
|
|
> the <A HREF="26_1_Glossary.html#symbol"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>symbol</EM
|
||
|
|
></A
|
||
|
|
>’s <A HREF="26_1_Glossary.html#value_cell"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>value cell</EM
|
||
|
|
></A
|
||
|
|
>.</P
|
||
|
|
></DD
|
||
|
|
><DT
|
||
|
|
><B
|
||
|
|
>Examples</B
|
||
|
|
></DT
|
||
|
|
><DD
|
||
|
|
><PRE CLASS="screen"
|
||
|
|
>(setf (symbol-value 'a) 1) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 1
|
||
|
|
(symbol-value 'a) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 1
|
||
|
|
;; SYMBOL-VALUE cannot see lexical variables.
|
||
|
|
(let ((a 2)) (symbol-value 'a)) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 1
|
||
|
|
(let ((a 2)) (setq a 3) (symbol-value 'a)) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 1
|
||
|
|
;; SYMBOL-VALUE can see dynamic variables.
|
||
|
|
(let ((a 2))
|
||
|
|
(declare (special a))
|
||
|
|
(symbol-value 'a)) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 2
|
||
|
|
(let ((a 2))
|
||
|
|
(declare (special a))
|
||
|
|
(setq a 3)
|
||
|
|
(symbol-value 'a)) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 3
|
||
|
|
(let ((a 2))
|
||
|
|
(setf (symbol-value 'a) 3)
|
||
|
|
a) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 2
|
||
|
|
a <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 3
|
||
|
|
(symbol-value 'a) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 3
|
||
|
|
(let ((a 4))
|
||
|
|
(declare (special a))
|
||
|
|
(let ((b (symbol-value 'a)))
|
||
|
|
(setf (symbol-value 'a) 5)
|
||
|
|
(values a b))) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 5, 4
|
||
|
|
a <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 3
|
||
|
|
(symbol-value :any-keyword) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> :ANY-KEYWORD
|
||
|
|
(symbol-value 'nil) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> NIL
|
||
|
|
(symbol-value '()) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> NIL
|
||
|
|
;; The precision of this next one is <A HREF="26_1_Glossary.html#implementation-dependent"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>implementation-dependent</EM
|
||
|
|
></A
|
||
|
|
>.
|
||
|
|
(symbol-value 'pi) <SPAN CLASS="cmsy"
|
||
|
|
><SPAN CLASS="arrow"
|
||
|
|
>→</SPAN
|
||
|
|
></SPAN
|
||
|
|
> 3.141592653589793d0</PRE
|
||
|
|
></DD
|
||
|
|
><DT
|
||
|
|
><B
|
||
|
|
>Affected By</B
|
||
|
|
></DT
|
||
|
|
><DD
|
||
|
|
><P CLASS="j"
|
||
|
|
><A HREF="f_makunbound.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>makunbound</B
|
||
|
|
></A
|
||
|
|
>, <A HREF="f_set.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>set</B
|
||
|
|
></A
|
||
|
|
>, <A HREF="f_setq.html" CLASS="specref"
|
||
|
|
><B
|
||
|
|
>setq</B
|
||
|
|
></A
|
||
|
|
></P
|
||
|
|
></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
|
||
|
|
><P CLASS="j"
|
||
|
|
>Should signal <A HREF="t_unbound-variable.html" CLASS="typeref"
|
||
|
|
><B
|
||
|
|
>unbound-variable</B
|
||
|
|
></A
|
||
|
|
> if <VAR CLASS="param"
|
||
|
|
>symbol</VAR
|
||
|
|
> is <A HREF="26_1_Glossary.html#unbound"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>unbound</EM
|
||
|
|
></A
|
||
|
|
> and an attempt is made to <A HREF="26_1_Glossary.html#read"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>read</EM
|
||
|
|
></A
|
||
|
|
> its <A HREF="26_1_Glossary.html#value"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>value</EM
|
||
|
|
></A
|
||
|
|
>. (No such error is signaled on an attempt to <A HREF="26_1_Glossary.html#write"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>write</EM
|
||
|
|
></A
|
||
|
|
> its <A HREF="26_1_Glossary.html#value"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>value</EM
|
||
|
|
></A
|
||
|
|
>.)</P
|
||
|
|
></DD
|
||
|
|
><DT
|
||
|
|
><B
|
||
|
|
>See Also</B
|
||
|
|
></DT
|
||
|
|
><DD
|
||
|
|
><P CLASS="j"
|
||
|
|
><A HREF="f_boundp.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>boundp</B
|
||
|
|
></A
|
||
|
|
>, <A HREF="f_makunbound.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>makunbound</B
|
||
|
|
></A
|
||
|
|
>, <A HREF="f_set.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>set</B
|
||
|
|
></A
|
||
|
|
>, <A HREF="f_setq.html" CLASS="specref"
|
||
|
|
><B
|
||
|
|
>setq</B
|
||
|
|
></A
|
||
|
|
></P
|
||
|
|
></DD
|
||
|
|
><DT
|
||
|
|
><B
|
||
|
|
>Notes</B
|
||
|
|
></DT
|
||
|
|
><DD
|
||
|
|
><P CLASS="j"
|
||
|
|
><A HREF="f_symbol-value.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>symbol-value</B
|
||
|
|
></A
|
||
|
|
> can be used to get the value of a <A HREF="26_1_Glossary.html#constant_variable"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>constant variable</EM
|
||
|
|
></A
|
||
|
|
>. <A HREF="f_symbol-value.html" CLASS="funref"
|
||
|
|
><B
|
||
|
|
>symbol-value</B
|
||
|
|
></A
|
||
|
|
> cannot <A HREF="26_1_Glossary.html#access"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>access</EM
|
||
|
|
></A
|
||
|
|
> the value of a <A HREF="26_1_Glossary.html#lexical_variable"
|
||
|
|
><EM CLASS="term"
|
||
|
|
>lexical variable</EM
|
||
|
|
></A
|
||
|
|
>.</P
|
||
|
|
></DD
|
||
|
|
></DL
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV CLASS="footer"
|
||
|
|
><DIV CLASS="btmnav"
|
||
|
|
><A HREF="f_symbol-plist.html" CLASS="prev"
|
||
|
|
>←</A
|
||
|
|
><A HREF="f_get.html" CLASS="next"
|
||
|
|
>→</A
|
||
|
|
></DIV
|
||
|
|
><DIV CLASS="trail"
|
||
|
|
>Conversion to HTML copyright 2023 by Gilbert Baumann</DIV
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><SCRIPT
|
||
|
|
>domReady();</SCRIPT
|
||
|
|
></BODY
|
||
|
|
></HTML
|
||
|
|
>
|