# phpman > perldoc > HTML::Mason::Lexer

## NAME
    [HTML::Mason::Lexer](https://www.chedong.com/phpMan.php/perldoc/HTML%3A%3AMason%3A%3ALexer/markdown) - Generates events based on component source lexing

## SYNOPSIS
      my $lexer = [HTML::Mason::Lexer](https://www.chedong.com/phpMan.php/perldoc/HTML%3A%3AMason%3A%3ALexer/markdown)->new;

      $lexer->lex( comp_source => $source, name => $comp_name, compiler => $compiler );

## DESCRIPTION
    The Lexer works in tandem with the Compiler to turn Mason component source into something else,
    generally Perl code.

    As the lexer finds component elements, like a tag or block, it calls the appropriate event
    methods in the compiler object it was given.

    It has only a few public methods.

    You can replace this lexer with one of your own simply by telling the Compiler to use a
    different lexer class. Your lexer class simply needs to call the appropriate methods in the
    Component Class's API as it scans the source.

## METHODS
    The lexer has very few public methods.

    new This method creates a new Lexer object. This methods takes no parameters.

    lex ( comp_source => ..., name => ..., compiler => ... )
        This method tells the lexer to start scanning the given component source. All of these
        parameters are required. The "name" parameter will be used in any error messages generated
        during lexing. The "compiler" object must be an object that implements the Mason Component
        API.

    line_number
        The current line number that the lexer has reached.

    name
        The name of the component currently being lexed.

    throw_syntax_error ($error)
        This throws an "[HTML::Mason::Exception::Syntax](https://www.chedong.com/phpMan.php/perldoc/HTML%3A%3AMason%3A%3AException%3A%3ASyntax/markdown)" error with the given error message as well
        as additional information about the component source.

        This method is used by both the Lexer and the Compiler.

## SUBCLASSING
    Any subclass of the lexer should declare itself to be a subclass of "[HTML::Mason::Lexer](https://www.chedong.com/phpMan.php/perldoc/HTML%3A%3AMason%3A%3ALexer/markdown)", even
    if it plans to override all of its public methods.

    If you want your subclass to work with the existing Compiler classes in Mason, you must
    implement the methods listed above. If you plan to use a custom Compiler class that you're
    writing, you can do whatever you want.

    We recommend that any parameters you add to Lexer be read-only, because the compiler object_id
    is only computed once on creation and would not reflect any changes to Lexer parameters.