Re: Spellcheck.adb

[Albert Bachmann <albert.bachmann@gmx.de>]

On Wed, 27 Apr 2005 11:11:06 -0400, Matthew Heaney wrote:
> 
> "Albert Bachmann" <albert.bachmann@gmx.de> wrote in message 
> news:1114548638.851249.246280@f14g2000cwb.googlegroups.com...
>>
>> In the meantime I followed the advice from Matthew Heaney (thanks
>> Matthew) and went on with  Ada.Containers. I again tried a simple
>> implementation. Unfortunately I recognized that controlled types have
>> to be instantiated at library level
> 
> This is no longer true in Ada 2005.  Eventually you'll be able to 
> instantiate the containers in your main subprogram.

That may be true but with GNAT (as of GCC-4.0.0) I get an error:

gcc -c -gnat05 -O3 spellcheck3.adb
spellcheck3.adb:10:09: instantiation error at a-cohata.ads:29
spellcheck3.adb:10:09: instantiation error at a-cihase.ads:214
spellcheck3.adb:10:09: controlled type must be declared at the library level
gnatmake: "spellcheck3.adb" compilation error

> 
> 
>> which requires now a total of 3
>> files since the instantiation of ada.containers.hashed_maps needs a
>> definite subtype for its key_type.
> 
> True, but that's why we have the Indefinite_Hashed_Maps container package. 
> If you're manipulating strings, you should probably be using that.
> 
> Also, as I mentioned in an earlier post, you don't really need a map, since 
> all you're doing is performing a membership test.  Hence, a (hashed) set 
> will do.
> 

When I use and instance of indefinite_hashed_sets or
indefinite_hashed_maps the program compiles fine but I get an exception
during runtime:

raised CONSTRAINT_ERROR : a-cihama.adb:443 explicit raise (for the map)
raised CONSTRAINT_ERROR : a-cihase.adb:375 explicit raise (for the set)


>> types.ads:
>> ----------
>>
>> package types is
>> subtype word is string(1 .. 128);
>> end types;
> 
> Get rid of this.  Instantiate the Indefinite_Hashed_Sets (or _Maps, if you 
> prefer) with type String.
> 

Ok.

> 
>> hashmap.ads:
>> ------------
>>
>> package hashmap is new ada.containers.hashed_maps(key_type  =>
>> types.word,
> 
> No.  This should just be type String.
> 

Ok.

> 
>> and finally spellcheck2.adb:
>> ----------------------------
>>
>> strings.fixed.delete(item, item_offset + 1, word'last);
> 
> You can get rid of this.

I did.
> 
> 
>> hashmap.insert(dict, item, true);
> 
> If you used a (hashed) set, then all you'd have to say is
> 
>   insert(dict, item);
> 
> 
>> strings.fixed.delete(item, item_offset + 1, word'last);
> 
> You can get rid of this.
> 

Here too.

> 
>> if not hashmap.contains(dict, item) then
> 
> See, you're not using the map element at all.  You're only using the key.
> 
> 
>> Please note that those attempts are only quick and dirty hacks. If
>> someone knows how to get rid of the seperate types.ads file I would
>> welcome his advice.
> 
> You can get rid of the types file, by using the indefinite hashed map (or 
> set), and instantiating it with type String.
> 
> -Matt

I post the modified source. Maybe I've overlooked something because as I
said above during runtime I get an exception. However thanks for those
valuable information Matthew!

hashed_set.ads:
--------------

with ada.containers.indefinite_hashed_sets;
with ada.strings.hash;
--with hash_function;

package hashed_set is new ada.containers.indefinite_hashed_set(
				element_type    => string,
				hash            => ada.strings.hash, --hash_function,
				equivalent_keys => "=");

spellcheck3.adb:
----------------

with ada.strings.fixed;
with ada.text_io;
with hashed_set;
use  ada;

procedure spellcheck3 is

	file        : text_io.file_type;
	item        : string(1 .. 128);
	item_offset : natural;
	dict        : hashed_set.set;

begin

	text_io.open(file, text_io.in_file, "spellcheck-dict.txt");
	
	while not text_io.end_of_file(file) loop
		text_io.get_line(file, item, item_offset);
		hashed_set.insert(dict, item);
	end loop;

	while not text_io.end_of_file loop
		text_io.get_line(item, item_offset);
		if not hashed_set.contains(dict, item) then
			text_io.put_line(item);
		end if;
	end loop;
	
	text_io.close(file);

end spellcheck3;


Regards,
Albert