Mfcttrf

Often I am typing equations with many Greek characters in them, and it becomes cumbersome to type out the commands for them all. I would like to make a command or environment that replaces Latin characters with analogous Greek ones. For example, something like greekabge or begingreekabgeendgreek would display the same as alphabetagammaepsilon.

I've tried making letters active so that I can use something like let aalpha, but the problem with that approach is that then I can't use them as part of commands - I'd like to be able to have something like greekadotbge display as greekalphadotbetagammaepsilon.

I also tried using DeclareUnicodeCharacter to replace e.g. a with the alpha character, but I get an error because the unicode value of a is less than 00A0. Is there some other way I can make this work?

Fill in the table:

documentclassarticle

newcommandgreek[1]begingroupsetuplatintogreek#1endgroup

newcommandsetuplatintogreek%
 mathcode`a=alpha
 mathcode`b=beta
 mathcode`g=gamma
 mathcode`d=delta
 mathcode`e=varepsilon
 %...


begindocument

$abgde+greekabgde$

enddocument

This is just the kind of problem for which the tokcycle package was made.

I've only implemented a handfull of the Greek, but you just need a tcmapto zzeta type statement for each new mapping. In the MWE, I also use |...| to escape characters back to the original Latin. Macros are automatically intercepted and preserved with the Latin interpretation of the name. All grouping considerations of the greek environment are preserved in the transformed output.

documentclassarticle
usepackagetokcycle
tokcycleenvironmentgreek
addcytoks[4]tcremap##1
processtoks##1
addcytoks##1
addcytoks##1
newcommand*tcmapto[2]expandafterdefcsname tcmapto#1endcsname#2
newcommand*tcremap[1]ifcsname tcmapto#1endcsname
 csname tcmapto#1expandafterendcsnameelseexpandafter#1fi
tcmapto aalpha tcmapto bbeta tcmapto eepsilon 
tcmapto ggamma tcmapto ppi
begindocument
[
y = greek a^2bfrac2eg + p^endgreek + x
]
enddocument

I edited the answer to NOT make use of expanded since not everyone has an updated TeX installation. So, addcytoks[4]... indicates to perform 4 expansions on the argument before storing the result, which is sufficient here to achieve the goal. The alternate syntax of addcytoks[x]... invokes expanded on the argument before storing the result. With the [x] option, the tcremap macro can also be simplified, by eliminating the expandafters as such: newcommand*tcremap[1]ifcsname tcmapto#1endcsnamecsname tcmapto#1endcsnameelse#1fi

Note: MikTeX doesn't quite load the package properly. You will have to manually download tokcycle.tex to your localtexmf at texgenerictokcycletokcycle.tex. See https://www.ctan.org/pkg/tokcycle