This has been semi-automatically converted from hfst-ospell software's README file.

Hfst-ospell library and toy commandline tester

This is a minimal hfst optimized lookup format based spell checker library and a demonstrational implementation of command line based spell checker. The library is licenced under Apache licence version 2, other licences can be obtained from University of Helsinki.


  • libxml++2
  • libarchive

Debian packages for dependencies

  • libxml++2-dev
  • libarchive-dev


Usage in external programs::

    #include <ospell.h>

and compile your project with::

    $(pkg-config --cflags hfstospell)

and link with::

    $(pkg-config --libs hfstospell)

Programming examples

The library lives in a namespace called hfst_ol. Pass (weighted!) Transducer pointers to the Speller constructor, eg.::

    FILE * error_source = fopen(error_filename, "r");
    FILE * lexicon_file = fopen(lexicon_filename, "r");
    hfst_ol::Transducer * error;
    hfst_ol::Transducer * lexicon;
    try {
        error = new hfst_ol::Transducer(error_source);
        lexicon = new hfst_ol::Transducer(lexicon_file);
    } catch (hfst_ol::TransducerParsingException& e) {
            /* problem with transducer file, usually completely
            different type of file - there's no magic number
            in the header to check for this */
    hfst_ol::Speller * speller;
    try {
        speller = new hfst_ol::Speller(error, lexicon);
    } catch (hfst_ol::AlphabetTranslationException& e) {
        /* problem with translating between the two alphabets */

And use the functions::

    // returns true if line is found in lexicon
    bool hfst_ol::Speller::check(char * line);

    // CorrectionQueue is a priority queue, sorted by weight
    hfst_ol::CorrectionQueue hfst_ol::Speller::correct(char * line);

to communicate with it. See main.cc for a concrete usage example.

Command-line tool

Main.cc provides a demo utility with the following help message::

    Usage: hfst-ospell [OPTIONS] ERRORSOURCE LEXICON
    Run a composition of ERRORSOURCE and LEXICON on standard input and
    print corrected output

      -h, --help                  Print this help message
      -V, --version               Print version information
      -v, --verbose               Be verbose
      -q, --quiet                 Don't be verbose (default)
      -s, --silent                Same as quiet

    Report bugs to hfst-bugs@ling.helsinki.fi

Use in real-world applications

The HFST based spellers can be used in real applications with help of `voikko <http://voikko.sf.net>`_. Voikko in turn can be used with enchant, libreoffice, and firefox.

Topic revision: r1 - 2012-07-05 - TommiPirinen
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