The main function.

def main():
    """The main function."""
    
    # Find the current Boost source-directory in which this script is located.
    sourceDir = current_boost_dir()
    if sourceDir == None:
        sourceDir = ""
    
    # Prepare and run cmdline-parser.
    cmdlineParser = argparse.ArgumentParser(description="A generator-script for pre-processed Boost.MPL headers.")
    cmdlineParser.add_argument("-v", "--verbose", dest='verbose', action='store_true',
                               help="Be a little bit more verbose.")
    cmdlineParser.add_argument("-s", "--sequence-type", dest='seqType', choices=['variadic', 'numbered', 'both'],
                               default='both',
                               help="Only update pre-processed headers for the selected sequence types, "
                                    "either 'numbered' sequences, 'variadic' sequences or 'both' sequence "
                                    "types. (Default=both)")
    cmdlineParser.add_argument("--no-vector", dest='want_vector', action='store_false',
                               help="Do not update pre-processed headers for Boost.MPL Vector.")
    cmdlineParser.add_argument("--no-list", dest='want_list', action='store_false',
                               help="Do not update pre-processed headers for Boost.MPL List.")
    cmdlineParser.add_argument("--no-set", dest='want_set', action='store_false',
                               help="Do not update pre-processed headers for Boost.MPL Set.")
    cmdlineParser.add_argument("--no-map", dest='want_map', action='store_false',
                               help="Do not update pre-processed headers for Boost.MPL Map.")
    cmdlineParser.add_argument("--num-elements", dest='numElements', metavar="<num-elements>",
                               type=to_positive_multiple_of_10, default=100,
                               help="The maximal number of elements per container sequence. (Default=100)")
    cmdlineParser.add_argument(dest='sourceDir', metavar="<source-dir>", default=current_boost_dir(), nargs='?',
                               type=to_existing_absolute_path,
                               help="The source-directory of Boost. (Default=\"" + sourceDir + "\")")
    args = cmdlineParser.parse_args()

    # Some verbose debug output.
    if args.verbose:
        print "Arguments extracted from command-line:"
        print "  verbose          = ", args.verbose
        print "  source directory = ", args.sourceDir
        print "  num elements     = ", args.numElements
        print "  sequence type    = ", args.seqType
        print "  want: vector     = ", args.want_vector
        print "  want: list       = ", args.want_list
        print "  want: set        = ", args.want_set
        print "  want: map        = ", args.want_map

    # Verify that we received any source-directory.
    if args.sourceDir == None:
        print "You should specify a valid path to the Boost source-directory."
        sys.exit(0)

    # The directories for header- and source files of Boost.MPL.
    # NOTE: Assuming 'args.sourceDir' is the source-directory of the entire boost project.
    headerDir = os.path.join( args.sourceDir, "boost", "mpl" )
    sourceDir = os.path.join( args.sourceDir, "libs", "mpl", "preprocessed" )
    # Check that the header/source-directories exist.
    if not os.path.exists( headerDir ) or not os.path.exists( sourceDir ):
        # Maybe 'args.sourceDir' is not the source-directory of the entire boost project
        # but instead of the Boost.MPL git-directory, only?
        headerDir = os.path.join( args.sourceDir, "include", "boost", "mpl" )
        sourceDir = os.path.join( args.sourceDir, "preprocessed" )
        if not os.path.exists( headerDir ) or not os.path.exists( sourceDir ):
            cmdlineParser.print_usage()
            print "error: Cannot find Boost.MPL header/source files in given Boost source-directory!"
            sys.exit(0)

    # Some verbose debug output.
    if args.verbose:
        print "Chosen header-directory: ", headerDir
        print "Chosen source-directory: ", sourceDir

    # Create list of containers for which files shall be pre-processed.
    containers = []
    if args.want_vector:
        containers.append('vector')
    if args.want_list:
        containers.append('list')
    if args.want_set:
        containers.append('set')
    if args.want_map:
        containers.append('map')
    if containers == []:
        print "Nothing to do."
        print "(Why did you prevent generating pre-processed headers for all Boost.MPL container types?)"
        sys.exit(0)

    # Possibly fix the header-comments of input-files needed for pre-processing.
    if args.verbose:
        print "Checking if prior to pre-processing some input-files need fixing."
    needFixing = fixmpl.check_input_files(headerDir, sourceDir, containers, args.seqType, args.verbose)
    if needFixing:
        if args.verbose:
            print "Fixing of some input-files prior to pre-processing is needed."
            print "Will fix them now!"
        fixmpl.fix_input_files(headerDir, sourceDir, containers, args.seqType, args.verbose)

    # Some verbose debug output.
    if args.verbose:
        print "Containers for which to pre-process headers: ", containers

    # Create (additional) input files for generating pre-processed headers of numbered sequence MPL containers.
    if args.seqType == "both" or args.seqType == "numbered":
        create_input_for_numbered_sequences(headerDir, sourceDir, containers, args.numElements)
    # Modify settings for generating pre-processed headers of variadic sequence MPL containers.
    if args.seqType == "both" or args.seqType == "variadic":
        adjust_container_limits_for_variadic_sequences(headerDir, containers, args.numElements)

    # Generate MPL-preprocessed files.
    os.chdir( sourceDir )
    if args.seqType == "both" or args.seqType == "numbered":
        if args.want_vector:
            if args.verbose:
                print "Pre-process headers for Boost.MPL numbered vectors."
            os.system( "python " + os.path.join( sourceDir, "preprocess_vector.py" ) + " all " + args.sourceDir )
        if args.want_list:
            if args.verbose:
                print "Pre-process headers for Boost.MPL numbered lists."
            os.system( "python " + os.path.join( sourceDir, "preprocess_list.py" ) + " all " + args.sourceDir )
        if args.want_set:
            if args.verbose:
                print "Pre-process headers for Boost.MPL numbered sets."
            os.system( "python " + os.path.join( sourceDir, "preprocess_set.py" ) + " all " + args.sourceDir )
        if args.want_map:
            if args.verbose:
                print "Pre-process headers for Boost.MPL numbered maps."
            os.system( "python " + os.path.join( sourceDir, "preprocess_map.py" ) + " all " + args.sourceDir )
    if args.seqType == "both" or args.seqType == "variadic":
        if args.verbose:
            print "Pre-process headers for Boost.MPL variadic containers."
        os.system( "python " + os.path.join( sourceDir, "preprocess.py" ) + " all " + args.sourceDir )