PACKAGE COMMANDS

::pt::peg::import objectName

This command creates a new import manager object with an associated Tcl command whose name is objectName. This object command is explained in full detail in the sections Object command and Object methods. The object command will be created under the current namespace if the objectName is not fully qualified, and in the specified namespace otherwise.

OBJECT COMMAND

All objects created by the ::pt::peg::import command have the following general form:

objectName method ?arg arg ...?

The method method and its arg'uments determine the exact behavior of the command. See section Object methods for the detailed specifications.

OBJECT METHODS

objectName destroy

This method destroys the object it is invoked for.

objectName import text text ?format?

This method takes the text and converts it from the specified format to the canonical serialization of a parsing expression grammar using the import plugin for the format. An error is thrown if no plugin could be found for the format. The serialization generated by the conversion process is returned as the result of this method.

If no format is specified the method defaults to text.

The specification of what a canonical serialization is can be found in the section PEG serialization format.

The plugin has to conform to the interface documented in the Parser Tools Import API specification.

objectName import file path ?format?

This method is a convenient wrapper around the import text method described by the previous item. It reads the contents of the specified file into memory, feeds the result into import text and returns the resulting serialization as its own result.

objectName import object text object text ?format?

This method is a convenient wrapper around the import text method described by the previous item. It expects that object is an object command supporting a deserialize method expecting the canonical serialization of a parsing expression grammar. It imports the text using import text and then feeds the resulting serialization into the object via deserialize. This method returns the empty string as it result.

objectName import object file object path ?format?

This method behaves like import object text, except that it reads the text to convert from the specified file instead of being given it as argument.

objectName includes

This method returns a list containing the currently specified paths to use to search for include files when processing input. The order of paths in the list corresponds to the order in which they are used, from first to last, and also corresponds to the order in which they were added to the object.

objectName include add path

This methods adds the specified path to the list of paths to use to search for include files when processing input. The path is added to the end of the list, causing it to be searched after all previously added paths. The result of the command is the empty string.

The method does nothing if the path is already known.

objectName include remove path

This methods removes the specified path from the list of paths to use to search for include files when processing input. The result of the command is the empty string.

The method does nothing if the path is not known.

objectName include clear

This method clears the list of paths to use to search for include files when processing input. The result of the command is the empty string.

EXAMPLE

Assuming the following PEG for simple mathematical expressions

PEG calculator (Expression)


    Digit      <- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9'	;


    Sign       <- '-' / '+'					;


    Number     <- Sign? Digit+					;


    Expression <- '(' Expression ')' / (Factor (MulOp Factor)*)	;


    MulOp      <- '*' / '/'					;


    Factor     <- Term (AddOp Term)*				;


    AddOp      <- '+'/'-'					;


    Term       <- Number					;
END;

then its canonical serialization (except for whitespace) is

pt::grammar::peg {


    rules {
	AddOp      {is {/ {t -} {t +}}                                                                mode value}
	Digit      {is {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}}                mode value}
	Expression {is {/ {x {t (} {n Expression} {t )}} {x {n Factor} {* {x {n MulOp} {n Factor}}}}} mode value}
	Factor     {is {x {n Term} {* {x {n AddOp} {n Term}}}}                                        mode value}
	MulOp      {is {/ {t *} {t /}}                                                                mode value}
	Number     {is {x {? {n Sign}} {+ {n Digit}}}                                                 mode value}
	Sign       {is {/ {t -} {t +}}                                                                mode value}
	Term       {is  {n Number}                                                                    mode value}


    }


    start {n Expression}
}

EXAMPLE

Assuming the parsing expression shown on the right-hand side of the rule

    Expression <- '(' Expression ')'


                / Factor (MulOp Factor)*

then its canonical serialization (except for whitespace) is

    {/ {x {t (} {n Expression} {t )}} {x {n Factor} {* {x {n MulOp} {n Factor}}}}}