Next: Through A Pipe, Up: Writing programs to use Aspell [Contents]
The Aspell library contains two main classes and several helper
classes. The two main classes are AspellConfig and
AspellSpeller. The AspellConfig class is used to set
initial defaults and to change spell checker specific options. The
AspellSpeller class does most of the real work. The
C API is responsible for managing the dictionaries, checking
if a word is in the dictionary, and coming up with suggestions among
other things. There are many helper classes the important ones are
AspellWordList, AspellMutableWordList,
Aspell*Enumeration. The AspellWordList classes is used
for accessing the suggestion list, as well as the personal and
suggestion word list currently in use. The
AspellMutableWordList is used to manage the personal, and
perhaps other, word lists. The Aspell*Enumeration classes are
used for iterating through a list.
To use Aspell your application should include aspell.h. In
order to ensure that all the necessary libraries are linked in libtool
should be used to perform the linking. When using libtool simply
linking with -laspell should be all that is necessary. When
using shared libraries you might be able to simply link
-laspell, but this is not recommended. This version of Aspell
uses the CVS version of libtool however released versions of libtool
should also work.
When your application first starts you should get a new configuration class with the command:
AspellConfig * spell_config = new_aspell_config();
which will create a new AspellConfig class. It is allocated
with new and it is your responsibility to delete it with
delete_aspell_config. Once you have the config class you
should set some variables. The most important one is the language
variable. To do so use the command:
aspell_config_replace(spell_config, "lang", "en_US");
which will set the default language to use to American English. The language is expected to be the standard two letter ISO 639 language code, with an optional two letter ISO 3166 country code after an underscore. You can set the preferred size via the size option, any extra info via the variety option, and the encoding via the encoding option. Other things you might want to set is the preferred spell checker to use, the search path for dictionaries, and the like — see The Options, for a list of all available options.
Whenever a new document is created a new AspellSpeller class
should also be created. There should be one speller class per
document. To create a new speller class use the
new_aspell_speller and then cast it up using
to_aspell_speller like so:
AspellCanHaveError * possible_err = new_aspell_speller(spell_config); AspellSpeller * spell_checker = 0; if (aspell_error_number(possible_err) != 0) puts(aspell_error_message(possible_err)); else spell_checker = to_aspell_speller(possible_err);
which will create a new AspellSpeller class using the defaults
found in spell_config. To find out which dictionary is
selected the lang, size, and variety options
may be examined. To find out the exact name of the dictionary the
master option may be examined as well as the
master-flags options to see if there were any special flags
that were passed on to the module. The module option way
also be examined to figure out which speller module was selected, but
since there is only one this option will always be the same.
If for some reason you want to use different defaults simply clone
spell_config and change the setting like so:
AspellConfig * spell_config2 = aspell_config_clone(spell_config); aspell_config_replace(spell_config2, "lang","nl"); possible_err = new_aspell_speller(spell_config2); delete_aspell_config(spell_config2);
Once the speller class is created you can use the check method
to see if a word in the document is correct like so:
int correct = aspell_speller_check(spell_checker, word, size);
word is expected to be a const char * character string.
size is the length of the string or -1 if the string is
null terminated. aspell_speller_check will return 0 if it is not found
and non-zero otherwise.
If you are using the ucs-2 or ucs-4 encoding then the
string is expected to be either a 2 or 4 byte wide integer
(respectively) and the _w macro version should be used:
int correct = aspell_speller_check_w(spell_checker, word, size);
The macro will cast the string to to the correct type and convert
size into bytes for you and then a call the special wide version of the
function that will make sure the encoding is correct for the type
passed in. For compatibility with older versions of Aspell the normal
non-wide functions can still be used provided that the size of the
string, in bytes, is also passed in. Null terminated ucs-2 or
ucs-4 are no longer supported when using the non-wide functions.
If the word is not correct, then the suggest method can be used
to come up with likely replacements.
AspellWordList * suggestions = aspell_speller_suggest(spell_checker,
word, size);
AspellStringEnumeration * elements = aspell_word_list_elements(suggestions);
const char * word;
while ( (word = aspell_string_enumeration_next(aspell_elements)) != NULL )
{
// add to suggestion list
}
delete_aspell_string_enumeration(elements);
Notice how elements is deleted but suggestions is not.
The value returned by suggestions is only valid to the next
call to suggest.
If you are using the ucs-2 or ucs-4 encoding then, in
addition to using the _w macro for the suggest method, you
should also use the _w macro with the next method which
will cast the string to the correct type for you. For example, if you
are using the ucs-2 encoding and the string is a const
uint16_t * then you should use:
AspellWordList * suggestions = aspell_speller_suggest_w(spell_checker,
word, size);
AspellStringEnumeration * elements = aspell_word_list_elements(suggestions);
const uint16_t * word;
while ( (word = aspell_string_enumeration_next_w(uint16_t, aspell_elements)) != NULL )
{
// add to suggestion list
}
delete_aspell_string_enumeration(elements);
Once a replacement is made the
store_repl method should be used to communicate the replacement
pair back to the spell checker (for the reason, see Notes on Storing Replacement Pairs). Its usage is as follows:
aspell_speller_store_repl(spell_checker, misspelled_word, size,
correctly_spelled_word, size);
If the user decided to add the word to the session or personal
dictionary the the word can be be added using the
add_to_session or add_to_personal methods respectively
like so:
aspell_speller_add_to_session|personal(spell_checker, word, size);
It is better to let the spell checker manage these words rather than doing it yourself so that the words have a chance of appearing in the suggestion list.
Finally, when the document is closed the AspellSpeller class
should be deleted like so:
delete_aspell_speller(spell_checker);
Methods that return a boolean result generally return false on
error and true otherwise. To find out what went wrong use the
error_number and error_message methods. Unless
otherwise stated methods that return a const char * will return
NULL on error. In general, the character string returned is
only valid until the next method which returns a const char *
is called.
For the details of the various classes please see the header files. In the future I will generate class references using some automated tool.
Two simple examples are included in the examples directory. The
example-c program demonstrates most of the Aspell library
functionality and the list-dicts lists the available
dictionaries.
Aspell should be thread safe, when used properly, as long as the
underlying compiler, C and C++ library is thread safe. Aspell
objects, including the AspellSpeller class, should not be used by
multiple threads unless they are protected by locks or it is only
accessed by read-only methods. A method is read-only only if a
const object is passed in. Many methods that seam to be
read-only are not because they may store state information in the
object.
Next: Through A Pipe, Up: Writing programs to use Aspell [Contents]