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Updated string literals description to encompass Unicode literals and the 

additional escape sequences defined for Unicode.
This closes bug #117158.
This commit is contained in:
Fred Drake 2000-12-19 04:52:03 +00:00
parent 1367b83797
commit dea764d7f1
1 changed files with 24 additions and 11 deletions
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35
Doc/ref/ref2.tex
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@ -304,6 +304,9 @@ escapeseq: "\" <any ASCII character>
\end{verbatim} \end{verbatim}
\index{ASCII@\ASCII{}} \index{ASCII@\ASCII{}}
\index{triple-quoted string}
\index{Unicode Consortium}
\index{string!Unicode}
In plain English: String literals can be enclosed in matching single In plain English: String literals can be enclosed in matching single
quotes (\code{'}) or double quotes (\code{"}). They can also be quotes (\code{'}) or double quotes (\code{"}). They can also be
enclosed in matching groups of three single or double quotes (these enclosed in matching groups of three single or double quotes (these
@ -311,10 +314,12 @@ are generally referred to as \emph{triple-quoted strings}). The
backslash (\code{\e}) character is used to escape characters that backslash (\code{\e}) character is used to escape characters that
otherwise have a special meaning, such as newline, backslash itself, otherwise have a special meaning, such as newline, backslash itself,
or the quote character. String literals may optionally be prefixed or the quote character. String literals may optionally be prefixed
with a letter `r' or `R'; such strings are called raw strings and use with a letter `r' or `R'; such strings are called
different rules for backslash escape sequences. \dfn{raw strings}\index{raw string} and use different rules for
\index{triple-quoted string} backslash escape sequences. A prefix of 'u' or 'U' makes the string
\index{raw 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.
In triple-quoted strings, In triple-quoted strings,
unescaped newlines and quotes are allowed (and are retained), except unescaped newlines and quotes are allowed (and are retained), except
@ -339,25 +344,33 @@ to those used by Standard \C{}. The recognized escape sequences are:
\lineii{\e b} {\ASCII{} Backspace (BS)} \lineii{\e b} {\ASCII{} Backspace (BS)}
\lineii{\e f} {\ASCII{} Formfeed (FF)} \lineii{\e f} {\ASCII{} Formfeed (FF)}
\lineii{\e n} {\ASCII{} Linefeed (LF)} \lineii{\e n} {\ASCII{} Linefeed (LF)}
\lineii{\e N\{\var{name}\}}
{Character named \var{name} in the Unicode database (Unicode only)}
\lineii{\e r} {\ASCII{} Carriage Return (CR)} \lineii{\e r} {\ASCII{} Carriage Return (CR)}
\lineii{\e t} {\ASCII{} Horizontal Tab (TAB)} \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 v} {\ASCII{} Vertical Tab (VT)} \lineii{\e v} {\ASCII{} Vertical Tab (VT)}
\lineii{\e\var{ooo}} {\ASCII{} character with octal value \emph{ooo}} \lineii{\e\var{ooo}} {\ASCII{} character with octal value \var{ooo}}
\lineii{\e x\var{hh...}} {\ASCII{} character with hex value \emph{hh...}} \lineii{\e x\var{hh}} {\ASCII{} character with hex value \var{hh}}
\end{tableii} \end{tableii}
\index{ASCII@\ASCII{}} \index{ASCII@\ASCII{}}
In strict compatibility with Standard \C, up to three octal digits are In strict compatibility with Standard C, up to three octal digits are
accepted, but an unlimited number of hex digits is taken to be part of accepted, but an unlimited number of hex digits is taken to be part of
the hex escape (and then the lower 8 bits of the resulting hex number the hex escape (and then the lower 8 bits of the resulting hex number
are used in 8-bit implementations). are used in 8-bit implementations).
Unlike Standard \C{}, Unlike Standard \index{unrecognized escape sequence}C,
all unrecognized escape sequences are left in the string unchanged, all unrecognized escape sequences are left in the string unchanged,
i.e., \emph{the backslash is left in the string.} (This behavior is i.e., \emph{the backslash is left in the string}. (This behavior is
useful when debugging: if an escape sequence is mistyped, the useful when debugging: if an escape sequence is mistyped, the
resulting output is more easily recognized as broken.) resulting output is more easily recognized as broken.) It is also
\index{unrecognized escape sequence} important to note that the escape sequences marked as ``(Unicode
only)'' in the table above fall into the category of unrecognized
escapes for non-Unicode string literals.
When an `r' or `R' prefix is present, backslashes are still used to When an `r' or `R' prefix is present, backslashes are still used to
quote the following character, but \emph{all backslashes are left in quote the following character, but \emph{all backslashes are left in