On Wed, Feb 12, 2020 at 04:30:23PM +0100, Stephan Witt wrote:
> Am 12.02.2020 um 14:50 schrieb Scott Kostyshak <skost...@lyx.org>:
> >
> > On Wed, Feb 12, 2020 at 12:14:07PM +0100, Stephan Witt wrote:
> >> commit e900b61d46f02b2af9afcc697168e47e846b982d
> >> Author: Stephan Witt <sw...@lyx.org>
> >> Date: Wed Feb 12 12:32:31 2020 +0100
> >>
> >> Make cell index of tabular local for column loop.
> >> ---
> >> src/insets/InsetTabular.cpp | 4 +---
> >> 1 files changed, 1 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/src/insets/InsetTabular.cpp b/src/insets/InsetTabular.cpp
> >> index bc57e1a..7b4db19 100644
> >> --- a/src/insets/InsetTabular.cpp
> >> +++ b/src/insets/InsetTabular.cpp
> >> @@ -3024,8 +3024,6 @@ void Tabular::TeXRow(otexstream & os, row_type row,
> >> OutputParams const & runparams,
> >> list<col_type> columns, list<col_type> logical_columns)
> >> const
> >> {
> >> - idx_type cell = cellIndex(row, 0);
> >> -
> >> //output the top line
> >> TeXTopHLine(os, row, columns, logical_columns);
> >>
> >> @@ -3061,7 +3059,7 @@ void Tabular::TeXRow(otexstream & os, row_type row,
> >> if (isPartOfMultiColumn(row, c))
> >> continue;
> >>
> >> - cell = cellIndex(row, c);
> >> + idx_type cell = cellIndex(row, c);
> >>
> >> if (isPartOfMultiRow(row, c)
> >> && column_info[c].alignment != LYX_ALIGN_DECIMAL) {
> >
> > I just ask out curiosity (I still consider myself a beginner in C++):
> > Why make this change? I find the code with your change more readable: in
> > addition to clarifying that cell is used only inside of the for loop, it
> > also makes obvious that the value of cell from the previous iteration is
> > not used in the current iteration.
>
> IMO, readability is the biggest gain of this style.
> I’d like the scope of a variable to be as narrow as possible.That makes sense. > Another point the compiler mentioned: in case of the loop not > being entered the assignment before the loop is useless. Good point, I didn't think about that. > > Is it true that without optimization, this change would be less > > efficient because cell has to be recreated (so memory allocated) on each > > iteration of the for loop? But is the idea that compilers recognize this > > and only allocate memory once so that in practice there is no loss in > > efficiency? > > I cannot imagine that optimization of allocated memory is an issue. > I think the memory is allocated locally on stack anyway. Thanks for the explanation, Scott
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