Dear all,

I've been using Sage to try to display some graphical formulas, containing 
sums of pictures of graphs multiped by coefficients. The idea is to have 
something looking like the attached picture.

My idea for achieving this was to create a set of symbolic variables, one 
per graph, with the value latex_name set to some LaTeX code for drawing the 
graph (I already have code for generating the LaTeX from a given graph). 
Along the way I came across a few peculiarities which I haven't seen 
documented anywhere...

[ all of these tested using 'SageMath version 8.0, Release Date: 
2017-07-21'. Once built I will check against the latest version in git. ]

   - Creating variables with newlines in their LaTeX name. This works as 
   one might expect normally, but it seems to break down when displaying sums:


sage: test_var = SR.var('test_var', latex_name='\\text{Lorem}\n\\text{Ipsum 
dolor}')
sage: latex(test_var)
{\text{Lorem}
\text{Ipsum dolor}}
sage: latex(3*test_var)
3 \, {\text{Lorem}
\text{Ipsum dolor}}
sage: latex(test_var+3)
{\text{Lorem} + 3

Understandably, trying to display this last equation using view() generates 
an error.

   - Using the tightpage option. If one tries to include a pgfpicture 
   inside the latex_name, then the tightpage option (which defaults to True) 
   doesn't work:

sage: latex.add_package_to_preamble_if_available('pgf')
sage: test_var = SR.var('test_var', latex_name=r'\begin{pgfpicture} 
\pgfpathrectangle{\pgfpointorigin}{\pgfqpoint{1in}{1in}} 
\pgfusepath{stroke} \end{pgfpicture}')
sage: latex(test_var)
sage: view(test_var)
<tries to open an empty PDF document>
sage: view(test_var, tightpage=False)
<displays the picture on a full-sized page>

The cause of this seems to be the way that the tightpage module is used. 
The code in view() adds in '\PreviewEnvironment{page}' to the preamble, and 
sets the left and right math delimeters as '\begin{page}$' and 
'$\end{page}' respectively. However, in _latex_file (called by view), maths 
delimeters are not added when the string '\begin{pgfpicture}' appears. This 
could be remedied by perhaps having another pair of arguments to 
_latex_file called item_left and item_right, which are prepended and 
appended as needed. This leads on to:


   - Expressions involving numbers and pictures don't produce valid LaTeX 
   code. Extending the above code example to the following causes a LaTeX 
   error:
   
sage: latex.add_package_to_preamble_if_available('pgf')
sage: test_var = SR.var('test_var', latex_name=r'\begin{pgfpicture} 
\pgfpathrectangle{\pgfpointorigin}{\pgfqpoint{1in}{1in}} 
\pgfusepath{stroke} \end{pgfpicture}')
sage: latex(test_var)
sage: view(3/2 * test_var, tightpage=False)
<causes a LaTeX error>


As above, this is because maths delimiters are not added before and after 
the string, so the generated LaTeX, containing \frac{3}{2}, fails to 
compile. I can't think of an obvious solution other than the fact that 
pgfpicture should work perfectly well within a maths environment, so it may 
as well be added anyway.

I have looked on these mailing list and on Ask sage and I haven't found 
anything about these behaviours; I apologise if this is a duplicate of some 
post elsewhere.

Best wishes,
Peter Banks


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