Add new skew hadamard matrices

[MatteoCati]

Fixes #34848.

[dimpase]

@wdjoyner - you might look at the freshly built docs here: https://deploy-preview-35059--sagemath-tobias.netlify.app/

[dimpase]

by the way, for sage.combinat.matrices.hadamard_matrix.normalise_hadamard(H, skew=True) it would be good to have a test of what happens if you feed it a matrix which is not skew (and doesn't get skew by applying the code in the function)

[vbraun]

PDF docs don't build

[dimpase]

our usual unicode hiccup:

! Package inputenc Error: Unicode character ̌ (U+030C)
(inputenc)                not set up for use with LaTeX.

See the inputenc package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.2927 Publikacije Elektrotehnič
                                  kog fakulteta. Serija Matematika 2 (1992):...

? 
! Emergency stop.
 ...                                              
                                                  
l.2927 Publikacije Elektrotehnič
                                  kog fakulteta. Serija Matematika 2 (1992):...

!  ==> Fatal error occurred, no output PDF file produced!

[dimpase]

So this needs yet another \DeclareUnicodeCharacter in src/sage_docbuild/conf.py

[dimpase]

I don't know how to fix this in a regular way; i.e. I added

--- a/src/sage_docbuild/conf.py
+++ b/src/sage_docbuild/conf.py
@@ -620,6 +620,7 @@ latex_elements['preamble'] = r"""
     \DeclareUnicodeCharacter{256E}{+}
     \DeclareUnicodeCharacter{256F}{+}
     \DeclareUnicodeCharacter{2570}{+}
+    \DeclareUnicodeCharacter{030C}{\v{c}}              % č
 \fi
 
 \let\textLaTeX\LaTeX

but it had no effect.

Am I missing something, @vbraun ?

[dimpase]

hmm, U+030C is not č, it's a modifier which adds this decoration, maybe this is why... Trying replace with č (U+010D)

[dimpase]

trying to use xelatex instead of pdflatex now.

[dimpase]

@jhpalmieri - have you seen this sort of trouble before? How about switching to xelatex - any objection?

[dimpase]

with the last change, it works.
references.pdf

[dimpase]

there are two ways to get caron-accented characters in Unicode - we must you the one that encodes it as one unicode characater, not two. This is fixed now.

[jhpalmieri]

@jhpalmieri - have you seen this sort of trouble before? How about switching to xelatex - any objection?

It sounds like this has been resolved, but I'll reply anyway. I've never used xelatex, but if that works better, it's fine with me. Would it be crazy to switch everything to ConTeXt?

[github-actions]

Documentation preview for this PR is ready! 🎉
Built with commit: f3ac064