# Re: ddoc latex/formulas?

On 9/15/16 5:50 AM, Johan Engelen wrote:

On Wednesday, 14 September 2016 at 11:36:11 UTC, Andrei Alexandrescu wrote:

On 9/14/16 1:50 AM, Manu via Digitalmars-d wrote:

Can we produce formulas, or latex in ddoc? Are there any examples in
phobos I can refer to?



https://github.com/dlang/dlang.org/blob/master/latex.ddoc

That's the macros file for generating the language spec in LaTeX format.


I think what the man is asking for is a way to write formulas in DDoc,
regardless of output format. Foremost, the math should display well on
dlang.org.



I see. So he's referring to LaTeX macros as an _input_ method, not as a _generated_ conduit. Thanks!


A good answer to that would seem www.mathjax.org. I defined the DIP1000 semantics (bunch of judgments and greeks) in a ddoc file that uses mathjax. For a while (until crunch mode set in) I've used mathjax for https://arxiv.org/abs/1606.00484. I have a BigO paper (not yet published) that also uses MathJAX for producing consistent LaTeX/PDF and HTML documents from the same source.


If you look at https://dlang.org/phobos/std_mathspecial.html#.gamma,
there is some math there. But then if you look at the DDoc source,
https://github.com/dlang/phobos/blob/master/std/mathspecial.d, it's
pretty terrible how to get it done, and it is very limited (how would
you get "sqrt(x+y)" to display well, or probably what Manu wants, how to
get matrix math to display well?).



Here there seems to be a mix of input syntax and rendering being discussed. This confuses the living daylight of me again. Let me make sure I understand matters correctly:


* ddoc has absolutely nada notion of rendering. To ask "how do I render sqrt and aligned matrices with ddoc" does not compute. Is there agreement on that?


* mathjax (and latex from which its input syntax is inspired) offer a solution for both input (those \macros) and rendering.


* ddoc may be used with either mathjax or latex without interfering in any way. It's just a macro system.

So the way you mention to get some math input in ddoc in mathspecial is:

$(GAMMA)(z) =$(INTEGRATE 0, $(INFIN))$(POWER t, z-1)\$(POWER e, -t) dt


This input can be trivially rendered as mathjax/latex by defining the macros suitably. In LaTeX and MathJaX the input would be:

\Gamma(z) = \int_0^\infty \! t^{z-1} e^{-t} \mathrm{d}t


which... does not seem quite a day and night difference IMHO. Though I do prefer the latter for math-intensive docs because it's a tad more concise.


A great addition to DDoc would be to allow LaTeX bits, like doxygen
does, and render it nicely for both web and PDF output. You just mark a
piece of text as <LatexStartsHere>....<LatexOut>.



We already have that. Just use latex syntax inside  and import mathjax if you want to generate HTML, or do nothing else to generate LaTeX. I'm doing it all the time in my papers.


Andrei