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Add material about the "r" and "u" prefixes for string literals; should

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be reviewed for clarity.

Work around a bogosity in the HTML version of the escape sequences table
conversion.
This commit is contained in:
Fred Drake 2001-08-14 21:43:31 +00:00
parent 0cac5f697b
commit c0cf726d8c
1 changed files with 14 additions and 8 deletions
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22
Doc/ref/ref2.tex
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@ -311,7 +311,9 @@ String literals are described by the following lexical definitions:
\index{ASCII@\ASCII{}}
\begin{productionlist}
\production{stringliteral}
{\token{shortstring} | \token{longstring}}
{[\token{stringprefix}](\token{shortstring} | \token{longstring})}
\production{stringprefix}
{"r" | "u" | "ur" | "R" | "U" | "UR" | "Ur" | "uR"}
\production{shortstring}
{"'" \token{shortstringitem}* "'"
| '"' \token{shortstringitem}* '"'}
@ -325,11 +327,15 @@ String literals are described by the following lexical definitions:
\production{shortstringchar}
{<any ASCII character except "\e" or newline or the quote>}
\production{longstringchar}
{<any ASCII character except "\e">}
{<any ASCII characteru except "\e">}
\production{escapeseq}
{"\e" <any ASCII character>}
\end{productionlist}
One syntactic restriction not indicated by these productions is that
whitespace is not allowed between the \grammartoken{stringprefix} and
the rest of the string literal.
\index{triple-quoted string}
\index{Unicode Consortium}
\index{string!Unicode}
@ -340,12 +346,14 @@ are generally referred to as \emph{triple-quoted strings}). The
backslash (\code{\e}) character is used to escape characters that
otherwise have a special meaning, such as newline, backslash itself,
or the quote character. String literals may optionally be prefixed
with a letter `r' or `R'; such strings are called
\dfn{raw strings}\index{raw string} and use different rules for
with a letter `r' or `R'; such strings are called \dfn{raw
strings}\index{raw string} and use different rules for interpreting
backslash escape sequences. A prefix of 'u' or 'U' makes the string
a Unicode string. Unicode strings use the Unicode character set as
defined by the Unicode Consortium and ISO~10646. Some additional
escape sequences, described below, are available in Unicode strings.
The two prefix characters may be combined; in this case, `u' must
appear before `r'.
In triple-quoted strings,
unescaped newlines and quotes are allowed (and are retained), except
@ -374,10 +382,8 @@ to those used by Standard C. The recognized escape sequences are:
{Character named \var{name} in the Unicode database (Unicode only)}
\lineii{\e r} {\ASCII{} Carriage Return (CR)}
\lineii{\e t} {\ASCII{} Horizontal Tab (TAB)}
\lineii{\e u\var{xxxx}}
{Character with 16-bit hex value \var{xxxx} (Unicode only)}
\lineii{\e U\var{xxxxxxxx}}
{Character with 32-bit hex value \var{xxxxxxxx} (Unicode only)}
\lineii{\e u\var{xxxx}} {Character with 16-bit hex value \var{xxxx} (Unicode only)}
\lineii{\e U\var{xxxxxxxx}}{Character with 32-bit hex value \var{xxxxxxxx} (Unicode only)}
\lineii{\e v} {\ASCII{} Vertical Tab (VT)}
\lineii{\e\var{ooo}} {\ASCII{} character with octal value \var{ooo}}
\lineii{\e x\var{hh}} {\ASCII{} character with hex value \var{hh}}