xtc.parser
Class Transformer

java.lang.Object
  xtc.tree.Visitor
      xtc.parser.Transformer

public class Transformer
extends Visitor

Visitor to transform productions. This visitor lifts repetitions, options, and nested choices into their own productions, desugars reptitions and options, and adds the appropriate semantic values to expressions that require them. It also ensures that repeated, optional, and predicated elements are sequences, thus fulfilling the requirements for code generation. Before applying this visitor on a grammar, the grammar must have been simplified, all text-only productions should be marked as such by applying the TextTester visitor, and all token-level productions should be marked as such by applying the Tokenizer visitor. Note that Generifier adds the appropriate semantic values for generic productions. Further note that repetitions in transient productions are not desugared (nor lifted) if the corresponding command line option ("-Orepeated-Ooptional") is set. Finally, note that this visitor assumes that the entire grammar is contained in a single module.

This visitor may report errors to the user.

Version:

$Revision: 1.128 $

Author:

Robert Grimm

Nested Class Summary

class	Transformer.Deducer Visitor to add semantic values.
class	Transformer.Desugarer Visitor to desugar repetitions and options.
class	Transformer.Lifter Visitor to lift nested choices, repetitions, and options.
class	Transformer.Typer Visitor to deduce a production's type.

Field Summary

protected Analyzer	analyzer The analyzer.
protected AST	ast The type operations.
static java.lang.String	ELEMENT_MARKER The variable marker for bindings in repeated or optional elements.
protected boolean	hasParseTree The flag for whether the current module has the parseTree attribute.
protected FullProduction	production The current (full) production.
protected Runtime	runtime The runtime.

Constructor Summary

Transformer(Runtime runtime, Analyzer analyzer, AST ast)
Create a new transformer.

Method Summary

boolean	changesState() Determine whether the current production changes the global parser state.
protected Production	current() Get the current production.
protected boolean	isGeneric() Determine whether the current production is generic.
protected boolean	isLeftRecursive() Determine whether the current production is a directly left-recursive production.
protected boolean	isList() Determine whether the current production has a list value.
protected boolean	isMemoized() Determine whether the current production is memoized.
protected boolean	isTextOnly() Determine whether the current production is text-only.
protected boolean	isToken() Determine whether the current production is token-level.
protected boolean	isVoid() Determine whether the current production is void.
protected void	process(FullProduction p) Process the specified production.
protected boolean	retainOptions() Determine whether the current production may contain options.
protected boolean	retainRepetitions() Determine whether the current production may contain repetitions.
void	visit(FullProduction p) Visit the specified production.
void	visit(Module m) Visit the specified grammar.

Methods inherited from class xtc.tree.Visitor

dispatch, equals, hashCode, iterate, map, mapInPlace, unableToVisit, visit

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

ELEMENT_MARKER

public static final java.lang.String ELEMENT_MARKER

The variable marker for bindings in repeated or optional elements.

See Also:

Constant Field Values

runtime

protected final Runtime runtime

The runtime.

analyzer

protected final Analyzer analyzer

The analyzer.

ast

protected final AST ast

The type operations.

hasParseTree

protected boolean hasParseTree

The flag for whether the current module has the parseTree attribute.

production

protected FullProduction production

The current (full) production.

Constructor Detail

Transformer

public Transformer(Runtime runtime,
                   Analyzer analyzer,
                   AST ast)

Create a new transformer.

Parameters:

runtime - The runtime.

analyzer - The analyzer utility.

ast - The type operations.

Method Detail

process

protected void process(FullProduction p)

Process the specified production. This method may be called recursively while processing another production.

Parameters:

p - The production to process.

isMemoized

protected boolean isMemoized()

Determine whether the current production is memoized.

Returns:

true if the current production is memoized.

changesState

public boolean changesState()

Determine whether the current production changes the global parser state.

Returns:

true if the current production is resetting or stateful.

isVoid

protected boolean isVoid()

Determine whether the current production is void.

Returns:

true if the current production is void.

isTextOnly

protected boolean isTextOnly()

Determine whether the current production is text-only.

Returns:

true if the current production is text-only.

isToken

protected boolean isToken()

Determine whether the current production is token-level.

Returns:

true if the current production is token-level.

isGeneric

protected boolean isGeneric()

Determine whether the current production is generic.

Returns:

true if the current production is generic.

isList

protected boolean isList()

Determine whether the current production has a list value.

Returns:

true if the current production has a list value.

isLeftRecursive

protected boolean isLeftRecursive()

Determine whether the current production is a directly left-recursive production.

Returns:

true if the current production is directly left-recursive.

current

protected Production current()

Get the current production.

Returns:

The current production.

retainRepetitions

protected boolean retainRepetitions()

Determine whether the current production may contain repetitions.

Returns:

true if the production may contain repetitions.

retainOptions

protected boolean retainOptions()

Determine whether the current production may contain options.

Returns:

true if the production may contain options.

visit

public void visit(Module m)

Visit the specified grammar.

visit

public void visit(FullProduction p)

Visit the specified production.