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| -rw-r--r-- | Doc/ref/ref5.tex | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/Doc/ref/ref5.tex b/Doc/ref/ref5.tex index 1d2f6fe..46fdd6d 100644 --- a/Doc/ref/ref5.tex +++ b/Doc/ref/ref5.tex @@ -676,11 +676,10 @@ converted to a common type. \section{Comparisons\label{comparisons}} \index{comparison} -Contrary to \C, all comparison operations in Python have the same -priority, which is lower than that of any arithmetic, shifting or -bitwise operation. Also contrary to \C, expressions like -\code{a < b < c} have the interpretation that is conventional in -mathematics: +Unlike C, all comparison operations in Python have the same priority, +which is lower than that of any arithmetic, shifting or bitwise +operation. Also unlike C, expressions like \code{a < b < c} have the +interpretation that is conventional in mathematics: \indexii{C}{language} \begin{verbatim} @@ -708,11 +707,12 @@ perfectly legal (though perhaps not pretty). The forms \code{<>} and \code{!=} are equivalent; for consistency with C, \code{!=} is preferred; where \code{!=} is mentioned below -\code{<>} is also acceptable. At some point in the (far) future, -\code{<>} may become obsolete. +\code{<>} is also accepted. The \code{<>} spelling is considered +obsolescent. -The operators \texttt{"<", ">", "==", ">=", "<="}, and \texttt{"!="} compare -the values of two objects. The objects needn't have the same type. +The operators \code{<}, \code{>}, \code{==}, \code{>=}, \code{<=}, and +\code{!=} compare +the values of two objects. The objects need not have the same type. If both are numbers, they are coverted to a common type. Otherwise, objects of different types \emph{always} compare unequal, and are ordered consistently but arbitrarily. @@ -732,7 +732,8 @@ Numbers are compared arithmetically. \item Strings are compared lexicographically using the numeric equivalents (the result of the built-in function \function{ord()}) of their -characters. +characters. Unicode and 8-bit strings are fully interoperable in this +behavior. \item Tuples and lists are compared lexicographically using comparison of @@ -765,19 +766,19 @@ For the list, tuple types, \code{\var{x} in \var{y}} is true if and only if there exists such an index \var{i} such that \code{var{x} == \var{y}[\var{i}]} is true. -For the Unicode and string types, \code{\var{x} in \var{y}} is true if and only -if there exists such an index \var{i} such that -\code{var{x} == \var{y}[\var{i}]} is true. If \code{\var{x}} is not -a string of length \code{1} or a unicode object of length \code{1}, -a \exception{TypeError} exception is raised. +For the Unicode and string types, \code{\var{x} in \var{y}} is true if +and only if there exists an index \var{i} such that \code{\var{x} == +\var{y}[\var{i}]} is true. If \code{\var{x}} is not a string or +Unicode object of length \code{1}, a \exception{TypeError} exception +is raised. For user-defined classes which define the \method{__contains__()} method, \code{\var{x} in \var{y}} is true if and only if \code{\var{y}.__contains__(\var{x})} is true. For user-defined classes which do not define \method{__contains__()} and -do define \var{__getitem__}, \code{\var{x} in \var{y}} is true if and only -if there is a non-negative integer index \var{i} such that +do define \method{__getitem__()}, \code{\var{x} in \var{y}} is true if +and only if there is a non-negative integer index \var{i} such that \code{\var{x} == \var{y}[\var{i}]}, and all lower integer indices do not raise \exception{IndexError} exception. (If any other exception is raised, it is as if \keyword{in} raised that exception). |