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Mistakes in the "sequence types" page:

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* explanation for example with lists of lists made confusing use of
  the word "contains" to mean "is built out of".

* wrong formula for slices with step.  Is it ok to use LaTeX formulas
  (which become images in the html document)?  This version needs one
  because it's based on a fraction.  Just writing "\code{(j-i)/k}" here would
  be ambiguous because it looks like a rounding-down-to-the-previous-integer
  division, which is not what we need here.  Of course we could write
  "\code{float(j-i)/k}" but it just looks confusing.
This commit is contained in:
Armin Rigo 2004-11-04 11:29:09 +00:00
parent 99e5ce5cf4
commit 80adba6873
1 changed files with 9 additions and 6 deletions
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15
Doc/lib/libstdtypes.tex
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@ -501,10 +501,11 @@ In Python 2.3 and beyond, \var{x} may be a string of any length.
[[3], [3], [3]]
\end{verbatim}
What has happened is that \code{lists} is a list containing three
copies of the list \code{[[]]} (a one-element list containing an
empty list), but the contained list is shared by each copy. You can
create a list of different lists this way:
What has happened is that \code{[[]]} is a one-element list containing
an empty list, so all three elements of \code{[[]] * 3} are (pointers to)
this single empty list. Modifying any of the elements of \code{lists}
modifies this single list. You can create a list of different lists this
way:
\begin{verbatim}
>>> lists = [[] for i in range(3)]
@ -529,8 +530,10 @@ In Python 2.3 and beyond, \var{x} may be a string of any length.
\item[(5)] The slice of \var{s} from \var{i} to \var{j} with step
\var{k} is defined as the sequence of items with index
\code{\var{x} = \var{i} + \var{n}*\var{k}} such that \code{0}
\code{<=} \var{n} \code{<} \code{abs(i-j)}. If \var{i} or \var{j}
\code{\var{x} = \var{i} + \var{n}*\var{k}} such that
$0 \leq n < \frac{j-i}{k}$. In other words, the indices
are \code{i}, \code{i+k}, \code{i+2*k}, \code{i+3*k} and so on, stopping when
\var{j} is reached (but never including \var{j}). If \var{i} or \var{j}
is greater than \code{len(\var{s})}, use \code{len(\var{s})}. If
\var{i} or \var{j} are omitted then they become ``end'' values
(which end depends on the sign of \var{k}). Note, \var{k} cannot