# Unicode in the equations: pros and cons

Is there any pros and cons for using of Unicode (and vice versa) in LaTeX equations?

Consider two examples:

\lim_{h→0}∫_{x_0}^{x_0 + h}\frac{f(t)}{h} = f(x_0)

x_0 ⇔ ∀ 𝜀 > 0, ∃ 𝛿 > 0,(|x-x_0| < 𝛿 ⇒ |f(x)-f(x_0)| < 𝜀)


And without Unicode:

\lim\limits_{h \to 0}\int\limits_{x_0}^{x_0+h}\frac{f(t)}{h}=f(x_0)

x_0 \Leftrightarrow \forall\epsilon > 0, \exists\delta>0,(|x-x_0|<\delta \Rightarrow |f(x)-f(x_0)|<\epsilon)


With latest XeLaTeX the result is the same, so!, what's better?

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See some discussion here Is there a way to use unicode-math in a more limited fashion and also some of the discussion in this recent chat session: Why use LaTeX instead of Word. –  Alan Munn Dec 16 '12 at 20:35
Probably ε (U+03B5, GREEK SMALL LETTER EPSILON) should really be 𝜀 (U+1D700, MATHEMATICAL ITALIC SMALL EPSILON). –  egreg Dec 16 '12 at 20:40
I'm pretty sure this would raise portability issues beside the obnoxiousness of a (virtual) unicode keyboard... something Word tries hard to emulate with the effect of giving me the creeps... –  Count Zero Dec 16 '12 at 20:41
Sorry for the question, but how do you input unicode characters fast? Do you look for it in a table? This is not fast, I think. If not, which is the usual method used? –  Manuel Dec 17 '12 at 14:03
@Manuel: I'm using XCompose in Linux with this config. –  m0nhawk Dec 17 '12 at 15:28

There was a time that the general feeling was that people should use \"{o} or \'e markup "for portability and ease of editing tools" rather than use ö or é but now I suspect that more or less anyone writing non English documents uses [latin1] or [utf8] with inputenc or uses xelatex or luatex and native Unicode input.
Despite the above, there are some advantages to using markup over direct character input, other than just familiarity for people who grew up using punched cards. One example that it is much easier to check that various document norms and conventions are upheld. For example if you want a particular arrow style it's probably easier (by eye) to spot (say) \longrightarrow than to recognise the multitude of different Unicode arrows. Also it depends on your tools, but for most of the tools I have it is still quicker and easier to type \longrightarrow than ⟶. But note that editing tools can completely lose the distinction, allowing you to type \longrightarrow but entering ⟶which is one reason why I suspect, as noted above that Unicode in files will become the norm.
I would like to add an additional comment on using ö and ä instead of \"{o} and \"{a}: Non-QUERTY keyboards, having to accommodate all the accented characters that they do, have important TeX characters like {} and \ in comparatively inconvenient places, usually requiring the use of the AltGR key and the like. This can't be helped, really, but I'd rather not use three hard-to-reach keys when one (easy to reach, at that) will suffice. I agree about characters not found on your keyboard, though, such as arrows etc. –  Ingmar Mar 26 '13 at 10:09
“…newer users will find it harder to accept restricting to an ascii character set.” Or, you know, just non-ascii language users, regardless of how new they are, which is like ~95% of the worlds population ;-) –  morbusg Mar 26 '13 at 10:42