Can ゐ/ヰ be combined with ゃゅょ/ャュョ?


I'm writing a program which replaces kana characters with romaji, so that
`りょかん` becomes `ryokan` etc. I thus need to handle cases where ゃゅょ (or ャュョ)
combine with the preceding character.

My understanding is that they can combine with any `-i` kana character except
い or イ. On this basis, ゐゃ/ゐゅ/ゐょ (or ヰャ/ヰュ/ヰョ) are valid combinations, being
transliterated as **wya** , **wyu** , and **wyo** respectively.

I didn't find anything useful on [jisho.org](http://jisho.org), but Wiktionary
has a few examples:

  * [en.wiktionary.org](http://en.wiktionary.org/wiki/%E6%B0%B8) has **永** : よう (ゐゃう)
  * [ja.wiktionary.org](http://ja.wiktionary.org/wiki/%E6%B4%AB) has **洫** : キョク (クヰョク)
  * [Various other pages](http://ja.wiktionary.org/w/index.php?title=%E7%89%B9%E5%88%A5%3A%E6%A4%9C%E7%B4%A2&profile=default&search=%E3%83%B0%E3%83%A3&fulltext=Search) mention ヰャゥ, クヰャウ, クヰャゥ, and クヰャク

However, I'm not sure if these would be applicable to modern Japanese - I get
the impression that they may simply be historic spellings, and thus no longer
relevant.

**tl;dr:** Would `wya`/`wyu`/`wyo` be considered be _valid_ combinations (even
if they're never actually used) in modern Japanese?




ゐ, ヰ, ゑ, and ヱ are not used in modern Japanese; they have been obsolete for
almost 70 years. Most people do not even know how to type these characters
with a keyboard. If you're not interested in the historical spellings of
Japanese, you can safely ignore them altogether. (And serious support for
historical Japanese is bound to be a _huge_ task.)

Actually, these characters may appear in some recent proper nouns, for example
[ヱヴァンゲリヲン](http://www.evangelion.co.jp/3_0/index.html) and
[よゐこ](http://415yoiko.jp/), just because they look peculiar and eye-catching.
If you need to handle such cases, you can simply replace these characters with
え or い, respectively.

You can type ゐ with `wyi` and ゑ with `wye` using most IMEs, and this was a
[part of JIS
standard](http://ja.wikipedia.org/wiki/%E3%83%AD%E3%83%BC%E3%83%9E%E5%AD%97%E5%85%A5%E5%8A%9B#.E5.BF.85.E3.81.9A.E5.AE.9F.E8.A3.85.E3.81.97.E3.81.AA.E3.81.91.E3.82.8C.E3.81.B0.E3.81.84.E3.81.91.E3.81.AA.E3.81.84.E5.85.A5.E5.8A.9B.E6.96.B9.E5.BC.8F).
But I think these are more like shortcuts rather than pronunciation-based
transliterations.

I don't recall the exact combination of ヰャ/ヰュ/ヰョ used, even in the classic
literature classes when I was a high school student. And I have no idea what
`wya`, `wyu`, or `wyo` should produce—at least my ATOK gives nothing. Maybe
they were used somewhere in the Japanese history, but I doubt it's worth
supporting.




ゐゃ/ゐょ only appear in
[合拗音](https://ja.wikipedia.org/wiki/%E6%8B%97%E9%9F%B3#.E5.90.88.E6.8B.97.E9.9F.B3_2)
of archaic on'yomi system (ゐゅ isn't attested). Historically they were
representing sounds like `wya` and `wyo` but they're very rare pronunciations
in limited combinations ゐゃう ( _wyau_ ), くゐゃう ( _kwyau_ ), くゐゃく ( _kwyaku_ )
and くゐょく ( _kwyoku_ ) (maybe ゐょう ( _wyou_ ) and ゐょく ( _wyoku_ ) too, according
to [this
paper](http://repository.dl.itc.u-tokyo.ac.jp/dspace/bitstream/2261/9796/1/nihongo03_1.pdf)).

The biggest problem is those spellings were (re-)discovered after abolition of
historical orthography, that means, they have never been and will never be
used outside historical study. I personally think it's not worth supporting
but isn't a big deal to support too, as far as it won't break your other
parts.

* * *

PS  
Things like くゐゃう should theoretically be written with small-size ゐ, that
corresponds to ゎ in くゎ. The lack of this letter I think explains how we don't
use it.

**Update** : Some auxiliary small kana including the small ゐ was [encoded into
Unicode in 2019](https://en.wikipedia.org/wiki/Small_Kana_Extension), though
the font support is still scarce.

* * *

Further reference:
[鎌倉時代における日本漢字音の位相的研究](http://ir.lib.hiroshima-u.ac.jp/ja/list/HU_type/9070/item/15563)

