How do you translate 'avais and 'eus' in sentences featuring a plus que parfait construction?
I.e. how do you translate 'j'avais perdu mon chapeau' as opposed to 'j'eus perdu mon chapeau'?
Ouais, enfin chtai compris your question. I still only have in hard-copy Grévisse, not any student books.
So, what you want to say is "I had had this blahblah" right?
"J'avais eu perdu mon chapeau." It's a modal tense, so, it depends on exactly what you intend "J'ai eu," perfectly fine, but it depends on your intention as the speaker.
It's not something you'd say everyday, and it might not even be legal to say it.
But I don't want to look it up in Grévisse.
I'd suggest a different phrasing, because it doesn't make much sense like that. I might have misread your intent, and if so, I can clarify and revise.
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As an aside, I'd really recommend finding even an older edition of Grévisse. Very much the authorative guide to usage. I wish I could remember some less cumbersome titles, but they're generally expensive as well. But if you're a nerd for usage and grammar, Grévisse is the only book you need.
/*I'l add another edit: I grew up speaking a kind of hillbilly French with one set of grandparents, but it was not anything close to a textbook correct style, and with a very limited syntax and vocabulary, and by far my most learning came from studies and a graduate fellowship teaching at UP VII. So, any actual French speakers should correct me, even if they're Belgian. I'm 100% sure my opinions are correct, but I'm wrong about a lot of things. Aside from literary works or didactic speech, yes, I speak French, but it's the kind of wrong French you'd say while drinking beers at a café. I'd probably get punched in the face if I tried to put the groove on a woman of any social standing, most definitely. So, fair warning, I think I'm right, but others probably know better.*/