----- Messaggio Originale ----- Da: Ralph Becket <rafe@csse.unimelb.edu.au> Data: Lunedi', Settembre 22, 2008 4:49 am Oggetto: Re: [mercury-users] Inst problem with hash tables A: mercury-users@csse.unimelb.edu.au > What you need is something like this: > > :- func unsafe_promise_unique_hash_table(hash_table(K, V)::in) = > (hash_table(K, V)::hash_table_uo) is det. > > :- pragma foreign_proc("C", > unsafe_promise_unique_hash_table(HT0::in) = (HT::hash_table_uo), > [promise_pure, will_not_call_mercury], > " > HT = HT0; > "). > > I'm just testing a version of this which I've added to the hash_table > module. I'll let you know once it's been reviewed. Using this function I get no compiling errors but I haven't managed to save and load a hash table anyway. Consider this sample program: main(!IO) :- % generate a list like this [{"a",1},{"b",2}, ... ] % different_strings(500,1,Strings), add_ints(Strings,0,IStrings), % the ht is filled from the list using strings % as keys and ints as values % new_default(string_double_hash) = Table, fill_table(IStrings,Table,Table1), % write hash table to disk % io.open_binary_output("ht.dat",Res1,!IO), ( if Res1 = ok(HTdat) then io.write_binary(HTdat,Table1,!IO), io.close_binary_output(HTdat,!IO) else error("Cannot open ht.dat!") ), % reads the hash table back from disk and prints it % io.open_binary_input("ht.dat",Res2,!IO), ( if Res2 = ok(HTdat2) then io.read_binary(HTdat2,ResTab,!IO), ( if ResTab = ok(Table20) then unsafe_promise_unique_hash_table(Table20) = Table2, io.print(Table2,!IO) else error("Invalid ht.dat!") ), io.close_binary_output(HTdat2,!IO) else error("Cannot open ht.dat!") ). It is compiled with no errors but when run it reports the error "Invalid ht.dat". I think that the problem resides in the high-order term in the hash table structure. It is written to disk just as the string '<<predicate>>'. How can I fix this problem? Thanks! Cheers, Andrea Bini