hm. "An APL" sounds fine to me! i'd say that, grammatically, "APL" (and other acronyms) become independent from their expansions.
e.g. would you say that expressions like "the FBI's policy" or "multiple DUIs" are grammatically incorrect? expanding the acronym gives "The Federal Beaurau of Investigations's policy" and "multiple Driving Under the Influences" which sound wrong, but the original expression is fine.
The FBI stands for "The Federal Bureau of Investigation." "The FBI's policy," as such, is grammatically correct.
English isn't a common language in Poland, is it?
my english is fine, thanks. my point was: splicing the expansion of "DUI" into a sentence will often make it ungrammatical, but that doesn't matter, because the acronym functions as a separate thing. analogously, expanding "an APL" into "an <A Programming Language>" and calling it incorrect is a weird way to judge a sentence.
anyway, i guess i was just in the mood to argue about something pointless online! have a nice day :)
"An A Programming Language is a very compact programming language."
As described by the ever-pleasant Dijkstra:
"APL is a mistake, carried through to perfection. It is the language of the future for the programming techniques of the past"