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<H2 CLASS="section"><A NAME="htoc52">6.1</A>��Lexical conventions</H2><H4 CLASS="subsubsection">Blanks</H4><P>The following characters are considered as blanks: space, newline,
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horizontal tabulation, carriage return, line feed and form feed. Blanks are
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ignored, but they separate adjacent identifiers, literals and
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keywords that would otherwise be confused as one single identifier,
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literal or keyword.</P><H4 CLASS="subsubsection">Comments</H4><P>Comments are introduced by the two characters <TT>(*</TT>, with no
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intervening blanks, and terminated by the characters <TT>*)</TT>, with
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no intervening blanks. Comments are treated as blank characters.
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Comments do not occur inside string or character literals. Nested
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comments are handled correctly.</P><H4 CLASS="subsubsection">Identifiers</H4><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="ident"><FONT COLOR=maroon>ident</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>�(<I><A HREF="#letter"><FONT COLOR=maroon>letter</FONT></A></I>∣�<FONT COLOR=blue><TT>_</TT></FONT>)�{�<I><A HREF="#letter"><FONT COLOR=maroon>letter</FONT></A></I>∣�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>∣�<FONT COLOR=blue><TT>'</TT></FONT>�}��</TD></TR>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="letter"><FONT COLOR=maroon>letter</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>A</TT></FONT>�…�<FONT COLOR=blue><TT>Z</TT></FONT>�∣��<FONT COLOR=blue><TT>a</TT></FONT>�…�<FONT COLOR=blue><TT>z</TT></FONT></TD></TR>
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</TABLE><P>Identifiers are sequences of letters, digits, <TT>_</TT> (the underscore
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character), and <TT>'</TT> (the single quote), starting with a
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letter or an underscore.
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Letters contain at least the 52 lowercase and uppercase
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letters from the ASCII set. The current implementation
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also recognizes as letters all accented characters from the ISO
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8859-1 (“ISO Latin 1”) set. All characters in an identifier are
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meaningful. The current implementation accepts identifiers up to
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16000000 characters in length.</P><H4 CLASS="subsubsection">Integer literals</H4><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="integer-literal"><FONT COLOR=maroon>integer-literal</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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[<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�[<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0x</TT></FONT>∣�<FONT COLOR=blue><TT>0X</TT></FONT>)�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>A</TT></FONT>…<FONT COLOR=blue><TT>F</TT></FONT>∣�<FONT COLOR=blue><TT>a</TT></FONT>…<FONT COLOR=blue><TT>f</TT></FONT>)
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{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>A</TT></FONT>…<FONT COLOR=blue><TT>F</TT></FONT>∣�<FONT COLOR=blue><TT>a</TT></FONT>…<FONT COLOR=blue><TT>f</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�[<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0o</TT></FONT>∣�<FONT COLOR=blue><TT>0O</TT></FONT>)�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>7</TT></FONT>)�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>7</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�[<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0b</TT></FONT>∣�<FONT COLOR=blue><TT>0B</TT></FONT>)�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>1</TT></FONT>)�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>1</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}</TD></TR>
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</TABLE><P>An integer literal is a sequence of one or more digits, optionally
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preceded by a minus sign. By default, integer literals are in decimal
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(radix 10). The following prefixes select a different radix:
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</P><DIV CLASS="center"><TABLE BORDER=1 CELLSPACING=0 CELLPADDING=1 WIDTH="80%"><TR><TD ALIGN=center NOWRAP><B>Prefix</B></TD><TD ALIGN=center NOWRAP><B>Radix</B></TD></TR>
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<TR><TD ALIGN=left NOWRAP>
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<TT>0x</TT>, <TT>0X</TT></TD><TD ALIGN=left NOWRAP>hexadecimal (radix 16)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>0o</TT>, <TT>0O</TT></TD><TD ALIGN=left NOWRAP>octal (radix 8)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>0b</TT>, <TT>0B</TT></TD><TD ALIGN=left NOWRAP>binary (radix 2)</TD></TR>
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(The initial <TT>0</TT> is the digit zero; the <TT>O</TT> for octal is the letter O.)
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The interpretation of integer literals that fall outside the range of
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representable integer values is undefined.</P><P>For convenience and readability, underscore characters (<TT>_</TT>) are accepted
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(and ignored) within integer literals.</P><H4 CLASS="subsubsection">Floating-point literals</H4><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="float-literal"><FONT COLOR=maroon>float-literal</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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[<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}�[<FONT COLOR=blue><TT>.</TT></FONT>�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}]
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[(<FONT COLOR=blue><TT>e</TT></FONT>∣�<FONT COLOR=blue><TT>E</TT></FONT>)�[<FONT COLOR=blue><TT>+</TT></FONT>∣�<FONT COLOR=blue><TT>-</TT></FONT>]�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)�{�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>�}]</TD></TR>
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</TABLE><P>Floating-point decimals consist in an integer part, a decimal part and
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an exponent part. The integer part is a sequence of one or more
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digits, optionally preceded by a minus sign. The decimal part is a
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decimal point followed by zero, one or more digits.
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The exponent part is the character <TT>e</TT> or <TT>E</TT> followed by an
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optional <TT>+</TT> or <TT>-</TT> sign, followed by one or more digits.
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The decimal part or the exponent part can be omitted, but not both to
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avoid ambiguity with integer literals.
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The interpretation of floating-point literals that fall outside the
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range of representable floating-point values is undefined.</P><P>For convenience and readability, underscore characters (<TT>_</TT>) are accepted
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(and ignored) within floating-point literals.</P><H4 CLASS="subsubsection">Character literals</H4><P>
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<A NAME="s:characterliteral"></A></P><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="char-literal"><FONT COLOR=maroon>char-literal</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=blue><TT>'</TT></FONT>�<FONT COLOR=maroon><I>regular-char</I></FONT>�<FONT COLOR=blue><TT>'</TT></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>'</TT></FONT>�<I><A HREF="#escape-sequence"><FONT COLOR=maroon>escape-sequence</FONT></A></I>�<FONT COLOR=blue><TT>'</TT></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="escape-sequence"><FONT COLOR=maroon>escape-sequence</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=blue><TT>\</TT></FONT>�(<FONT COLOR=blue><TT>\</TT></FONT>�∣��<FONT COLOR=blue><TT>"</TT></FONT>�∣��<FONT COLOR=blue><TT>'</TT></FONT>�∣��<FONT COLOR=blue><TT>n</TT></FONT>�∣��<FONT COLOR=blue><TT>t</TT></FONT>�∣��<FONT COLOR=blue><TT>b</TT></FONT>�∣��<FONT COLOR=blue><TT>r</TT></FONT>)
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>\</TT></FONT>�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>)
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>\x</TT></FONT>�(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>A</TT></FONT>…<FONT COLOR=blue><TT>F</TT></FONT>∣�<FONT COLOR=blue><TT>a</TT></FONT>…<FONT COLOR=blue><TT>f</TT></FONT>)
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(<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>A</TT></FONT>…<FONT COLOR=blue><TT>F</TT></FONT>∣�<FONT COLOR=blue><TT>a</TT></FONT>…<FONT COLOR=blue><TT>f</TT></FONT>)</TD></TR>
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</TABLE><P>Character literals are delimited by <TT>'</TT> (single quote) characters.
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The two single quotes enclose either one character different from
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<TT>'</TT> and <TT>\</TT>, or one of the escape sequences below:
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</P><DIV CLASS="center"><TABLE BORDER=1 CELLSPACING=0 CELLPADDING=1 WIDTH="80%"><TR><TD ALIGN=center NOWRAP><B>Sequence</B></TD><TD ALIGN=center NOWRAP><B>Character denoted</B></TD></TR>
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<TR><TD ALIGN=left NOWRAP>
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<TT>\\</TT></TD><TD ALIGN=left NOWRAP>backslash (<TT>\</TT>)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\"</TT></TD><TD ALIGN=left NOWRAP>double quote (<TT>"</TT>)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\'</TT></TD><TD ALIGN=left NOWRAP>single quote (<TT>'</TT>)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\n</TT></TD><TD ALIGN=left NOWRAP>linefeed (LF)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\r</TT></TD><TD ALIGN=left NOWRAP>carriage return (CR)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\t</TT></TD><TD ALIGN=left NOWRAP>horizontal tabulation (TAB)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\b</TT></TD><TD ALIGN=left NOWRAP>backspace (BS)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\</TT><I>space</I></TD><TD ALIGN=left NOWRAP>space (SPC)</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\</TT><I>ddd</I></TD><TD ALIGN=left NOWRAP>the character with ASCII code <I>ddd</I> in decimal</TD></TR>
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<TR><TD ALIGN=left NOWRAP><TT>\x</TT><I>hh</I></TD><TD ALIGN=left NOWRAP>the character with ASCII code <I>hh</I> in hexadecimal</TD></TR>
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</TABLE></DIV><H4 CLASS="subsubsection">String literals</H4><P>
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<A NAME="s:stringliteral"></A></P><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="string-literal"><FONT COLOR=maroon>string-literal</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=blue><TT>"</TT></FONT>�{�<I><A HREF="#string-character"><FONT COLOR=maroon>string-character</FONT></A></I>�}�<FONT COLOR=blue><TT>"</TT></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="string-character"><FONT COLOR=maroon>string-character</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=maroon><I>regular-char-str</I></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�<I><A HREF="#escape-sequence"><FONT COLOR=maroon>escape-sequence</FONT></A></I></TD></TR>
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</TABLE><P>String literals are delimited by <TT>"</TT> (double quote) characters.
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The two double quotes enclose a sequence of either characters
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different from <TT>"</TT> and <TT>\</TT>, or escape sequences from the
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table given above for character literals.</P><P>To allow splitting long string literals across lines, the sequence
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<TT>\</TT><I>newline</I>�<I>blanks</I> (a <TT>\</TT> at end-of-line followed by any
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number of blanks at the beginning of the next line) is ignored inside
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string literals.</P><P>The current implementation places practically no restrictions on the
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length of string literals.</P><H4 CLASS="subsubsection">Naming labels</H4><P>To avoid ambiguities, naming labels cannot just be defined
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syntactically as the sequence of the three tokens <TT>~</TT>, <I><A HREF="#ident"><FONT COLOR=maroon>ident</FONT></A></I> and
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<TT>:</TT>, and have to be defined at the lexical level.</P><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="label"><FONT COLOR=maroon>label</FONT></A></I>�</TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>~</TT></FONT>�(<FONT COLOR=blue><TT>a</TT></FONT>�…�<FONT COLOR=blue><TT>z</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>)�{�<I><A HREF="#letter"><FONT COLOR=maroon>letter</FONT></A></I>∣�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>∣�<FONT COLOR=blue><TT>'</TT></FONT>�}�<FONT COLOR=blue><TT>:</TT></FONT>��</TD></TR>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="optlabel"><FONT COLOR=maroon>optlabel</FONT></A></I>�</TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>?</TT></FONT>�(<FONT COLOR=blue><TT>a</TT></FONT>�…�<FONT COLOR=blue><TT>z</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>)�{�<I><A HREF="#letter"><FONT COLOR=maroon>letter</FONT></A></I>∣�<FONT COLOR=blue><TT>0</TT></FONT>…<FONT COLOR=blue><TT>9</TT></FONT>∣�<FONT COLOR=blue><TT>_</TT></FONT>∣�<FONT COLOR=blue><TT>'</TT></FONT>�}�<FONT COLOR=blue><TT>:</TT></FONT></TD></TR>
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</TABLE><P>Naming labels come in two flavours: <I><A HREF="#label"><FONT COLOR=maroon>label</FONT></A></I> for normal arguments and
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<I><A HREF="#optlabel"><FONT COLOR=maroon>optlabel</FONT></A></I> for optional ones. They are simply distinguished by their
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first character, either <TT>~</TT> or <TT>?</TT>.</P><H4 CLASS="subsubsection">Prefix and infix symbols</H4><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="infix-symbol"><FONT COLOR=maroon>infix-symbol</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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(<FONT COLOR=blue><TT>=</TT></FONT>�∣��<FONT COLOR=blue><TT><</TT></FONT>�∣��<FONT COLOR=blue><TT>></TT></FONT>�∣��<FONT COLOR=blue><TT>@</TT></FONT>�∣��<FONT COLOR=blue><TT>^</TT></FONT>�∣��<FONT COLOR=blue><TT>|</TT></FONT>�∣��<FONT COLOR=blue><TT>&</TT></FONT>�∣�
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<FONT COLOR=blue><TT>+</TT></FONT>�∣��<FONT COLOR=blue><TT>-</TT></FONT>�∣��<FONT COLOR=blue><TT>*</TT></FONT>�∣��<FONT COLOR=blue><TT>/</TT></FONT>�∣��<FONT COLOR=blue><TT>$</TT></FONT>�∣��<FONT COLOR=blue><TT>%</TT></FONT>)�{�<I><A HREF="#operator-char"><FONT COLOR=maroon>operator-char</FONT></A></I>�}
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="prefix-symbol"><FONT COLOR=maroon>prefix-symbol</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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(<FONT COLOR=blue><TT>!</TT></FONT>�∣��<FONT COLOR=blue><TT>?</TT></FONT>�∣��<FONT COLOR=blue><TT>~</TT></FONT>)�{�<I><A HREF="#operator-char"><FONT COLOR=maroon>operator-char</FONT></A></I>�}
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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<TR><TD ALIGN=right NOWRAP>
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<I><A NAME="operator-char"><FONT COLOR=maroon>operator-char</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=blue><TT>!</TT></FONT>�∣��<FONT COLOR=blue><TT>$</TT></FONT>�∣��<FONT COLOR=blue><TT>%</TT></FONT>�∣��<FONT COLOR=blue><TT>&</TT></FONT>�∣��<FONT COLOR=blue><TT>*</TT></FONT>�∣��<FONT COLOR=blue><TT>+</TT></FONT>�∣��<FONT COLOR=blue><TT>-</TT></FONT>�∣��<FONT COLOR=blue><TT>.</TT></FONT>�∣�
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<FONT COLOR=blue><TT>/</TT></FONT>�∣��<FONT COLOR=blue><TT>:</TT></FONT>�∣��<FONT COLOR=blue><TT><</TT></FONT>�∣��<FONT COLOR=blue><TT>=</TT></FONT>�∣��<FONT COLOR=blue><TT>></TT></FONT>�∣��<FONT COLOR=blue><TT>?</TT></FONT>�∣��<FONT COLOR=blue><TT>@</TT></FONT>�∣�
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<FONT COLOR=blue><TT>^</TT></FONT>�∣��<FONT COLOR=blue><TT>|</TT></FONT>�∣��<FONT COLOR=blue><TT>~</TT></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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</TABLE><P>Sequences of “operator characters”, such as <TT><=></TT> or <TT>!!</TT>,
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are read as a single token from the <I><A HREF="#infix-symbol"><FONT COLOR=maroon>infix-symbol</FONT></A></I> or <I><A HREF="#prefix-symbol"><FONT COLOR=maroon>prefix-symbol</FONT></A></I>
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class. These symbols are parsed as prefix and infix operators inside
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expressions, but otherwise behave much as identifiers.
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</P><H4 CLASS="subsubsection">Keywords</H4><P>The identifiers below are reserved as keywords, and cannot be employed
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</P><PRE CLASS="verbatim"> and as assert asr begin class
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constraint do done downto else end
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exception external false for fun function
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functor if in include inherit initializer
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land lazy let lor lsl lsr
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lxor match method mod module mutable
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new object of open or private
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rec sig struct then to true
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try type val virtual when while
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</PRE><P>The following character sequences are also keywords:
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</P><PRE CLASS="verbatim"> != # & && ' ( ) * + , -
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-. -> . .. : :: := :> ; ;; <
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<- = > >] >} ? ?? [ [< [> [|
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] _ ` { {< | |] } ~
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</PRE><P>Note that the following identifiers are keywords of the Camlp4
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extensions and should be avoided for compatibility reasons.
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</P><PRE CLASS="verbatim"> parser << <: >> $ $$ $:
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</PRE><H4 CLASS="subsubsection">Ambiguities</H4><P>Lexical ambiguities are resolved according to the “longest match”
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rule: when a character sequence can be decomposed into two tokens in
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several different ways, the decomposition retained is the one with the
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longest first token.</P><H4 CLASS="subsubsection">Line number directives</H4><TABLE CLASS="display dcenter"><TR VALIGN="middle"><TD CLASS="dcell"><TABLE CELLSPACING=6 CELLPADDING=0><TR><TD ALIGN=right NOWRAP>
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<I><A NAME="linenum-directive"><FONT COLOR=maroon>linenum-directive</FONT></A></I></TD><TD ALIGN=center NOWRAP>::=</TD><TD ALIGN=left NOWRAP>
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<FONT COLOR=blue><TT>#</TT></FONT>�{<FONT COLOR=blue><TT>0</TT></FONT>�…�<FONT COLOR=blue><TT>9</TT></FONT>}<SUP>+</SUP>
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<TR><TD ALIGN=right NOWRAP> </TD><TD ALIGN=center NOWRAP>∣</TD><TD ALIGN=left NOWRAP>�<FONT COLOR=blue><TT>#</TT></FONT>�{<FONT COLOR=blue><TT>0</TT></FONT>�…�<FONT COLOR=blue><TT>9</TT></FONT>}<SUP>+</SUP>�<FONT COLOR=blue><TT>"</TT></FONT>�{�<I><A HREF="#string-character"><FONT COLOR=maroon>string-character</FONT></A></I>�}�<FONT COLOR=blue><TT>"</TT></FONT>
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<TR><TD ALIGN=right NOWRAP> </TD></TR>
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</TABLE><P>Preprocessors that generate Caml source code can insert line number
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directives in their output so that error messages produced by the
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compiler contain line numbers and file names referring to the source
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file before preprocessing, instead of after preprocessing.
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A line number directive is composed of a <TT>#</TT> (sharp sign), followed by
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a positive integer (the source line number), optionally followed by a
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character string (the source file name).
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Line number directives are treated as blank characters during lexical
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