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Diffstat (limited to 'Doc/ref/ref2.tex')
| -rw-r--r-- | Doc/ref/ref2.tex | 92 |
1 files changed, 56 insertions, 36 deletions
diff --git a/Doc/ref/ref2.tex b/Doc/ref/ref2.tex index 250bd2e..67f22f8 100644 --- a/Doc/ref/ref2.tex +++ b/Doc/ref/ref2.tex @@ -19,7 +19,7 @@ syntax (e.g. between statements in compound statements). \subsection{Comments} -A comment starts with a hash character (\verb\#\) that is not part of +A comment starts with a hash character (\verb@#@) that is not part of a string literal, and ends at the end of the physical line. A comment always signifies the end of the logical line. Comments are ignored by the syntax. @@ -28,7 +28,7 @@ the syntax. \index{physical line} \index{hash character} -\subsection{Line joining} +\subsection{Explicit line joining} Two or more physical lines may be joined into logical lines using backslash characters (\verb/\/), as follows: when a physical line ends @@ -37,15 +37,37 @@ joined with the following forming a single logical line, deleting the backslash and the following end-of-line character. For example: \index{physical line} \index{line joining} +\index{line continuation} \index{backslash character} % \begin{verbatim} -month_names = ['Januari', 'Februari', 'Maart', \ - 'April', 'Mei', 'Juni', \ - 'Juli', 'Augustus', 'September', \ - 'Oktober', 'November', 'December'] +if 1900 < year < 2100 and 1 <= month <= 12 \ + and 1 <= day <= 31 and 0 <= hour < 24 \ + and 0 <= minute < 60 and 0 <= second < 60: # Looks like a valid date + return 1 \end{verbatim} +A line ending in a backslash cannot carry a comment; a backslash does +not continue a comment (but it does continue a string literal, see +below). + +\subsection{Implicit line joining} + +Expressions in parentheses, square brackets or curly braces can be +split over more than one physical line without using backslashes. +For example: + +\begin{verbatim} +month_names = ['Januari', 'Februari', 'Maart', # These are the + 'April', 'Mei', 'Juni', # Dutch names + 'Juli', 'Augustus', 'September', # for the months + 'Oktober', 'November', 'December'] # of the year +\end{verbatim} + +Implicitly continued lines can carry comments. The indentation of the +continuation lines is not important. Blank continuation lines are +allowed. + \subsection{Blank lines} A logical line that contains only spaces, tabs, and possibly a @@ -123,7 +145,7 @@ The following example shows various indentation errors: (Actually, the first three errors are detected by the parser; only the last error is found by the lexical analyzer --- the indentation of -\verb\return r\ does not match a level popped off the stack.) +\verb@return r@ does not match a level popped off the stack.) \section{Other tokens} @@ -159,26 +181,15 @@ identifiers. They must be spelled exactly as written here: \index{reserved word} \begin{verbatim} -and del for in print -break elif from is raise -class else global not return -continue except if or try -def finally import pass while +access del from lambda return +and elif global not try +break else if or while +class except import pass +continue finally in print +def for is raise \end{verbatim} -% # This Python program sorts and formats the above table -% import string -% l = [] -% try: -% while 1: -% l = l + string.split(raw_input()) -% except EOFError: -% pass -% l.sort() -% for i in range((len(l)+4)/5): -% for j in range(i, len(l), 5): -% print string.ljust(l[j], 10), -% print +% When adding keywords, pipe it through keywords.py for reformatting \section{Literals} \label{literals} @@ -192,17 +203,24 @@ String literals are described by the following lexical definitions: \index{string literal} \begin{verbatim} -stringliteral: "'" stringitem* "'" -stringitem: stringchar | escapeseq -stringchar: <any ASCII character except newline or "\" or "'"> -escapeseq: "'" <any ASCII character except newline> +stringliteral: shortstring | longstring +shortstring: "'" shortstringitem* "'" | '"' shortstringitem* '"' +longstring: "'''" longstringitem* "'''" | '"""' longstringitem* '"""' +shortstringitem: shortstringchar | escapeseq +shortstringchar: <any ASCII character except "\" or newline or the quote> +longstringchar: <any ASCII character except "\"> +escapeseq: "\" <any ASCII character> \end{verbatim} \index{ASCII} -String literals cannot span physical line boundaries. Escape -sequences in strings are actually interpreted according to rules -similar to those used by Standard C. The recognized escape sequences -are: +In ``long strings'' (strings surrounded by sets of three quotes), +unescaped newlines and quotes are allowed (and are retained), except +that three unescaped quotes in a row terminate the string. (A +``quote'' is the character used to open the string, i.e. either +\verb/'/ or \verb/"/.) + +Escape sequences in strings are interpreted according to rules similar +to those used by Standard C. The recognized escape sequences are: \index{physical line} \index{escape sequence} \index{Standard C} @@ -211,8 +229,10 @@ are: \begin{center} \begin{tabular}{|l|l|} \hline +\verb/\/{\em newline} & Ignored \\ \verb/\\/ & Backslash (\verb/\/) \\ \verb/\'/ & Single quote (\verb/'/) \\ +\verb/\"/ & Double quote (\verb/"/) \\ \verb/\a/ & ASCII Bell (BEL) \\ \verb/\b/ & ASCII Backspace (BS) \\ %\verb/\E/ & ASCII Escape (ESC) \\ @@ -309,8 +329,8 @@ Some examples of floating point literals: \end{verbatim} Note that numeric literals do not include a sign; a phrase like -\verb\-1\ is actually an expression composed of the operator -\verb\-\ and the literal \verb\1\. +\verb@-1@ is actually an expression composed of the operator +\verb@-@ and the literal \verb@1@. \section{Operators} @@ -323,7 +343,7 @@ The following tokens are operators: < == > <= <> != >= \end{verbatim} -The comparison operators \verb\<>\ and \verb\!=\ are alternate +The comparison operators \verb@<>@ and \verb@!=@ are alternate spellings of the same operator. \section{Delimiters} |