[LyX/master] Make cell index of tabular local for column loop.

[Scott Kostyshak]

On Wed, Feb 12, 2020 at 12:14:07PM +0100, Stephan Witt wrote:
> commit e900b61d46f02b2af9afcc697168e47e846b982d
> Author: Stephan Witt <switt at 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.

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?

Scott
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