Pipe dreams for .latex()

.latex() is great! … but the output still requires a fair amount of editing to be truly useful/for it to save time.

This ticket may, as the name suggests, be unrealistically hopeful, but there are a few things that prevent .latex() from being fully useful:

• Fractions show up as decimals, which is kind of gross, and sometimes fails to capture the constraint in a recognizable form. Can we leverage the fractions library here to try to improve this?
• To complicate things more, there are irrational numbers that screw everything up. pi turns up all the time - is there anything we can implement that would recognize that a number is a multiple of pi and print accordingly?
• For obvious reasons, the exponents in a given constraint are applied to each variable separately. Again, this means that constraints may look weird. Can we group variables with the same exponent and wrap them in parentheses?
• This last one is definitely a pipe dream. The variables in a constraint are often (always?) printed in an order that is different from the way the constraint is typed, and therefore different from its recognizable form. If .latex() gives me 0.5 S C_d \rho V^2, I have to rearrange it to \frac12 \rho V^2 S C_d and this takes time. If I have to do this for every equation, I can probably achieve the same result by throwing some vim at the python source. Can anything be done about this?

Obviously, it won’t be possible to fully automate this for every single constraint ever, but I think the changes above, if at all possible, would make for a huge improvement, and drastically improve the usefulness of what is already a great concept.

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carry over from #780

• Currently the latex environment chosen does not support multi-page models, which is a problem for larger models. This might be best resolved by using a different environment (e.g. align).
• M. Drela suggests putting a small space between variables in monomials, if there is no exponent taking up space. This probably isn’t specific to the latex() method but that’s just where I noticed it.
• latex for some unit strings underscores letters after underscores. ex: pound_force_per_square_inch
• Create latex tables for models without needing to solve them (#1045)

[pgkirsch]

Eww do you really want to see your sensitivity to pi?

[bqpd]

https://github.com/convexengineering/gpkit/pull/1408 encompasses the first four points in the first post