''Surely you mean "if it doesn't rise then don't have bought it."?''

(Will Rogers, giving advice on buying stock.)

In Douglas Adams' TimeTravelGrammar, I think it's "Iffate it not rising, boughten it,"

Which book is ''that'' from?

'''Dr Dan Streetmentioner's Time Traveller's Handbook of 1001 Tense Formations'''

We hear about it in the Hitch-Hiker's Guide to the Galaxy universe (I'm spotty on the exact book) - I was just making the previous example up, using some of the syntax I remembered.  Then again, since he probably made up the words on the spot himself as he typed it, this is all a complete waste of time.  Is-being-forthwithenate.

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Heinlein postulated a similar convoluted grammar in GloryRoad (early 60s).

"Primer" is another relevant work   http://www.imdb.com/title/tt0390384/