ーるんじゃなかった = regret?

[Neil2]

Elsewhere I found:
朝ご飯を食べるんじゃなかった。
= lit. It is that breakfast wasn't to eat
= Should not have eaten breakfast, you know.
Can someone explain how this 'ーるんじゃなかった' structure demonstrates regret? Thanks in advance!

 

[Glenn]

It's the negated version of the のだ which shows that something is the thing to do (e.g., 急ぐんだ！; 学校が終わったらすぐ帰るんだ or something) put in past, to say "that was not the thing to do." That's basically it.

 

[Neil2]

I have never seen (and still can't) any mention of this use of んだ as meaning 'the thing to do' in my books or online. Do you know any links with more information?

 

[epigene]

I have never seen (and still can't) any mention of this use of んだ as meaning 'the thing to do' in my books or online. Do you know any links with more information?

Hope this page on verb conjugations help you:

Japanese Verb Conjugation

 

[Neil2]

Hope this page on verb conjugations help you:

That's a great site! Unfortunately, as far as I can see, all it says about んだ in this context is 'This form can also be used as an imperative (command).'

 

[epigene]

That's a great site! Unfortunately, as far as I can see, all it says about んだ in this context is 'This form can also be used as an imperative (command).'

This one?

Noun-related particles - Tae Kim's Japanese grammar guide

 

[Toritoribe]

See also the linked page below.(a J-J dictionary)

のだ
［連語］《準体助詞「の」＋断定の助動詞「だ」》

２ 話し手の決意、または相手に対する要求・詰問の意を表す。「なんとしてもその夢を実現させる― ◦だ」

[補説]話し言葉では「んだ」の形をとることが多い。

http://dictionary.goo.ne.jp/leaf/jn2/171961/m0u/のだ/

"The dictionary form of a volitional verb + んだ" expresses a strong command to the addressee or the speaker's determination. んじゃない is its negated version, thus, it means an order not to do~; "Don't~/You must not~".

朝ご飯を食べるんだ
You must eat breakfast.

朝ご飯を食べるんじゃない
You must not eat breakfast.

As Glenn-san explained, んじゃなかった can be considered as the past tense of this nagated form, "I shouldn't do at that time", i.e., "I actually did at that time and regret it now".

朝ご飯を食べるんじゃなかった
I shouldn't have eaten breakfast. (= I shouldn't eat breakfast at that time, but actually I ate and regret it now.)

Incidentally, んだ/んじゃない as a strong command can be used only for second person, similarly, んじゃなかった is only for the speaker's regret.

 

[Neil2]

Great. Thanks for your help folks.