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<!DOCTYPE HTML>
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>read-delimited-list | Common Lisp Nova Spec</TITLE
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>Common Lisp Nova Spec</A
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>→ <A HREF="23_Reader.html"
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>←</A
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>Apropos </SPAN
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><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);"
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><DIV CLASS="matter"
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><DIV CLASS="begincom"
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><HR
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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="read-delimited-list"
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></SPAN
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><B
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>read-delimited-list</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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>Function</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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>read-delimited-list</B
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> <SPAN CLASS="cmssi"
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>char</SPAN
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> <SPAN CLASS="cmtt"
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>&optional</SPAN
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> <SPAN CLASS="cmssi"
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>input-stream</SPAN
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> <SPAN CLASS="cmssi"
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>recursive-p</SPAN
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> <SPAN CLASS="arrow"
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>→</SPAN
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> <SPAN CLASS="cmssi"
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>list</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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>Arguments and Values</B
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></DT
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><DD
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><P CLASS="j"
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><VAR CLASS="param"
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>char</VAR
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> — a <A HREF="26_1_Glossary.html#character"
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><EM CLASS="term"
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>character</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>input-stream</VAR
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> — an <A HREF="26_1_Glossary.html#input"
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><EM CLASS="term"
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>input</EM
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></A
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> <A HREF="26_1_Glossary.html#stream_designator"
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><EM CLASS="term"
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>stream designator</EM
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></A
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>. The default is <A HREF="26_1_Glossary.html#standard_input"
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><EM CLASS="term"
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>standard input</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>recursive-p</VAR
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> — a <A HREF="26_1_Glossary.html#generalized_boolean"
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><EM CLASS="term"
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>generalized boolean</EM
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></A
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>. The default is <A HREF="26_1_Glossary.html#false"
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><EM CLASS="term"
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>false</EM
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></A
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>. </P
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><P CLASS="j"
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><VAR CLASS="param"
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>list</VAR
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> — a <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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> of the <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>objects</EM
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></A
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> read.</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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><A HREF="f_read-delimited-list.html" CLASS="funref"
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><B
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>read-delimited-list</B
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></A
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> reads <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>objects</EM
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></A
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> from <VAR CLASS="param"
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>input-stream</VAR
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> until the next character after an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
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>’s representation (ignoring <A HREF="26_1_Glossary.html#whitespace"
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><EM CLASS="term"
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>whitespace</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>2</SPAN
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></SUB
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></SPAN
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> characters and comments) is <VAR CLASS="param"
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>char</VAR
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>. </P
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><P CLASS="j"
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><A HREF="f_read-delimited-list.html" CLASS="funref"
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><B
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>read-delimited-list</B
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></A
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> looks ahead at each step for the next non-<A HREF="26_1_Glossary.html#whitespace"
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><EM CLASS="term"
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>whitespace</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>2</SPAN
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></SUB
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></SPAN
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> <A HREF="26_1_Glossary.html#character"
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><EM CLASS="term"
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>character</EM
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></A
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> and peeks at it as if with <A HREF="f_peek-char.html" CLASS="funref"
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><B
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>peek-char</B
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></A
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>. If it is <VAR CLASS="param"
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>char</VAR
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>, then the <A HREF="26_1_Glossary.html#character"
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><EM CLASS="term"
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>character</EM
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></A
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> is consumed and the <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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> of <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>objects</EM
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></A
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> is returned. If it is a <A HREF="26_1_Glossary.html#constituent"
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><EM CLASS="term"
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>constituent</EM
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></A
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> or <A HREF="26_1_Glossary.html#escape"
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><EM CLASS="term"
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>escape</EM
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></A
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> <A HREF="26_1_Glossary.html#character"
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><EM CLASS="term"
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>character</EM
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></A
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>, then <A HREF="f_read.html" CLASS="funref"
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><B
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>read</B
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></A
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> is used to read an <A HREF="26_1_Glossary.html#object"
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><EM CLASS="term"
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>object</EM
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></A
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>, which is added to the end of the <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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>. If it is a <A HREF="26_1_Glossary.html#macro_character"
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><EM CLASS="term"
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>macro character</EM
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></A
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>, its <A HREF="26_1_Glossary.html#reader_macro_function"
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><EM CLASS="term"
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>reader macro function</EM
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></A
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> is called; if the function returns a <A HREF="26_1_Glossary.html#value"
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><EM CLASS="term"
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>value</EM
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></A
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>, that <A HREF="26_1_Glossary.html#value"
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><EM CLASS="term"
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>value</EM
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></A
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> is added to the <A HREF="26_1_Glossary.html#list"
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><EM CLASS="term"
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>list</EM
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></A
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>. The peek-ahead process is then repeated. </P
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><P CLASS="j"
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>If <VAR CLASS="param"
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>recursive-p</VAR
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> is <A HREF="26_1_Glossary.html#true"
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><EM CLASS="term"
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>true</EM
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></A
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>, this call is expected to be embedded in a higher-level call to <A HREF="f_read.html" CLASS="funref"
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><B
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>read</B
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></A
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> or a similar function. </P
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><P CLASS="j"
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>It is an error to reach end-of-file during the operation of <A HREF="f_read-delimited-list.html" CLASS="funref"
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><B
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>read-delimited-list</B
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></A
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>. </P
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><P CLASS="j"
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>The consequences are undefined if <VAR CLASS="param"
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>char</VAR
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> has a <A HREF="26_1_Glossary.html#syntax_type"
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><EM CLASS="term"
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>syntax type</EM
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></A
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> of <A HREF="26_1_Glossary.html#whitespace"
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><EM CLASS="term"
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>whitespace</EM
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></A
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><SPAN CLASS="meaning"
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><SUB CLASS="sub"
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><SPAN CLASS="cmr"
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>2</SPAN
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></SUB
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></SPAN
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> in the <A HREF="26_1_Glossary.html#current_readtable"
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><EM CLASS="term"
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>current readtable</EM
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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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>Examples</B
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></DT
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><DD
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><PRE CLASS="screen"
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> (read-delimited-list #\<SPAN CLASS="cmr"
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>]</SPAN
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>) 1 2 3 4 5 6 <SPAN CLASS="cmr"
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>]</SPAN
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>
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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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> (1 2 3 4 5 6)</PRE
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><P CLASS="j"
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>Suppose you wanted <CODE CLASS="f"
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>#{<I CLASS="i"
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><I
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>a</I
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></I
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> <I CLASS="i"
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><I
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>b</I
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></I
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> <I CLASS="i"
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><I
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>c</I
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></I
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> <I
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>.</I
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> <I
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>.</I
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> <I
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>.</I
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> <I CLASS="i"
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><I
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>z</I
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></I
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>}</CODE
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> to read as a list of all pairs of the elements <I CLASS="i"
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><I
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>a</I
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></I
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>, <I CLASS="i"
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><I
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>b</I
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></I
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>, <I CLASS="i"
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><I
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>c</I
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></I
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>, <I
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>.</I
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> <I
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>.</I
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> <I
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>.</I
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>, <I CLASS="i"
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><I
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>z</I
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></I
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>, for example.</P
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><PRE CLASS="screen"
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>#{p q z a} reads as ((p q) (p z) (p a) (q z) (q a) (z a))</PRE
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><P CLASS="j"
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>This can be done by specifying a macro-character definition for <CODE CLASS="f"
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>#{</CODE
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> that does two things: reads in all the items up to the <CODE CLASS="f"
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>}</CODE
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>, and constructs the pairs. <A HREF="f_read-delimited-list.html" CLASS="funref"
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><B
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>read-delimited-list</B
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></A
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> performs the first task.</P
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><PRE CLASS="screen"
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>(defun |#{-reader| (stream char arg)
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(declare (ignore char arg))
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(mapcon #'(lambda (x)
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(mapcar #'(lambda (y) (list (car x) y)) (cdr x)))
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(read-delimited-list #\} stream t))) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> |#{-reader|
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(set-dispatch-macro-character #\# #\{ #'|#{-reader|) <SPAN CLASS="cmsy"
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><SPAN CLASS="arrow"
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>→</SPAN
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></SPAN
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> T
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(set-macro-character #\} (get-macro-character #\) <SPAN CLASS="misc"
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><B
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>nil</B
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></SPAN
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>))</PRE
|
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><P CLASS="j"
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>Note that <A HREF="26_1_Glossary.html#true"
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><EM CLASS="term"
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>true</EM
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></A
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> is supplied for the <VAR CLASS="param"
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>recursive-p</VAR
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> argument. </P
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><P CLASS="j"
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>It is necessary here to give a definition to the character <CODE CLASS="f"
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>}</CODE
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> as well to prevent it from being a constituent. If the line</P
|
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><PRE CLASS="screen"
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>(set-macro-character #\} (get-macro-character #\) <SPAN CLASS="misc"
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><B
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>nil</B
|
|
></SPAN
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>))</PRE
|
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><P CLASS="j"
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|
>shown above were not included, then the <CODE CLASS="f"
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>}</CODE
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> in</P
|
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><PRE CLASS="screen"
|
|
>#{ p q z a}</PRE
|
|
><P CLASS="j"
|
|
>would be considered a constituent character, part of the symbol named <CODE CLASS="f"
|
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>a}</CODE
|
|
>. This could be corrected by putting a space before the <CODE CLASS="f"
|
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>}</CODE
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>, but it is better to call <A HREF="f_set-macro-character.html" CLASS="funref"
|
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><B
|
|
>set-macro-character</B
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></A
|
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>. </P
|
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><P CLASS="j"
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>Giving <CODE CLASS="f"
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>}</CODE
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|
> the same definition as the standard definition of the character <CODE CLASS="f"
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>)</CODE
|
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> has the twin benefit of making it terminate tokens for use with <A HREF="f_read-delimited-list.html" CLASS="funref"
|
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><B
|
|
>read-delimited-list</B
|
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></A
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> and also making it invalid for use in any other context. Attempting to read a stray <CODE CLASS="f"
|
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>}</CODE
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> will signal an error.</P
|
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></DD
|
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><DT
|
|
><B
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|
>Affected By</B
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></DT
|
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><DD
|
|
><P CLASS="j"
|
|
><A HREF="v_debug-io.html" CLASS="varref"
|
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><B
|
|
>*standard-input*</B
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></A
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>, <A HREF="v_readtable.html" CLASS="varref"
|
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><B
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>*readtable*</B
|
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></A
|
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>, <A HREF="v_terminal-io.html" CLASS="varref"
|
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><B
|
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>*terminal-io*</B
|
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></A
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>.</P
|
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></DD
|
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><DT
|
|
><B
|
|
>See Also</B
|
|
></DT
|
|
><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_read.html" CLASS="funref"
|
|
><B
|
|
>read</B
|
|
></A
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|
>, <A HREF="f_peek-char.html" CLASS="funref"
|
|
><B
|
|
>peek-char</B
|
|
></A
|
|
>, <A HREF="f_read-char.html" CLASS="funref"
|
|
><B
|
|
>read-char</B
|
|
></A
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|
>, <A HREF="f_unread-char.html" CLASS="funref"
|
|
><B
|
|
>unread-char</B
|
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></A
|
|
>.</P
|
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></DD
|
|
><DT
|
|
><B
|
|
>Notes</B
|
|
></DT
|
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><DD
|
|
><P CLASS="j"
|
|
><A HREF="f_read-delimited-list.html" CLASS="funref"
|
|
><B
|
|
>read-delimited-list</B
|
|
></A
|
|
> is intended for use in implementing <A HREF="26_1_Glossary.html#reader_macro"
|
|
><EM CLASS="term"
|
|
>reader macros</EM
|
|
></A
|
|
>. Usually it is desirable for <VAR CLASS="param"
|
|
>char</VAR
|
|
> to be a <A HREF="26_1_Glossary.html#terminating"
|
|
><EM CLASS="term"
|
|
>terminating</EM
|
|
></A
|
|
> <A HREF="26_1_Glossary.html#macro_character"
|
|
><EM CLASS="term"
|
|
>macro character</EM
|
|
></A
|
|
> so that it can be used to delimit tokens; however, <A HREF="f_read-delimited-list.html" CLASS="funref"
|
|
><B
|
|
>read-delimited-list</B
|
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></A
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