xtc.parser
Class Inliner

java.lang.Object
  xtc.tree.Visitor
      xtc.parser.GrammarVisitor
          xtc.parser.Inliner

public class Inliner
extends GrammarVisitor

Visitor to inline productions. If cost-based inlining is enabled, this visitor inlines productions with a cost estimate less or equal to the maximum cost. However, to avoid changing a production's semantic value, cost-based inlining is limited to void, text-only, and token-level productions. Independent of whether cost-based inlining is enabled or not, this visitor inlines productions that are referenced from a production consisting solely of a nonterminal (which, optionally, may be bound to CodeGenerator.VALUE). Note that generic productions are never inlined; neither are productions with the state attribute.

Note that, to be effective, this visitor requires that text-only productions have been marked as such. Similarly, token-level productions need to have beeen marked as such. Further note that, if this visitor inlines productions, the resulting grammar needs to be simplified before further processing. Also note that this visitor may create new opportunities for the elimination of dead productions. This visitor assumes that the entire grammar is contained in a single module.

Version:

$Revision: 1.53 $

Author:

Robert Grimm

Field Summary

protected boolean	attributeState Flag for whether the grammar has the state attribute.
static boolean	INLINE_PERSISTENT The flag for whether to inline non-transient productions.
protected boolean	inlined Flag for whether this production inliner has inlined a production.
static int	MAX_COST The maximum cost for inlining productions at arbitrary positions.

Fields inherited from class xtc.parser.GrammarVisitor

analyzer, isBound, isLastElement, isPredicate, isRepeatedOnce, isTopLevel, isVoided, needsSequence, runtime, transformInPlace

Constructor Summary

Inliner(Runtime runtime, Analyzer analyzer)
Create a new production inliner.

Method Summary

protected void	inlined(Production p) Record that the specified production has been inlined and, if necessary, print a message to the console.
protected boolean	isBasic(Production p) Determine whether the specified production is void, text-only, or token-level.
java.lang.Object	visit(Module m) Process the specified grammar.
Element	visit(NonTerminal nt) Visit the specified nonterminal.

Methods inherited from class xtc.parser.GrammarVisitor

visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit

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

MAX_COST

public static final int MAX_COST

The maximum cost for inlining productions at arbitrary positions.

See Also:

Constant Field Values

INLINE_PERSISTENT

public static final boolean INLINE_PERSISTENT

The flag for whether to inline non-transient productions.

See Also:

Constant Field Values

attributeState

protected boolean attributeState

Flag for whether the grammar has the state attribute.

inlined

protected boolean inlined

Flag for whether this production inliner has inlined a production.

Constructor Detail

Inliner

public Inliner(Runtime runtime,
               Analyzer analyzer)

Create a new production inliner.

Parameters:

runtime - The runtime.

analyzer - The analyzer utility.

Method Detail

isBasic

protected boolean isBasic(Production p)

Determine whether the specified production is void, text-only, or token-level.

Parameters:

p - The production.

Returns:

true if the production is either text-only or void.

inlined

protected void inlined(Production p)

Record that the specified production has been inlined and, if necessary, print a message to the console.

Parameters:

p - The production.

visit

public java.lang.Object visit(Module m)

Process the specified grammar.

Overrides:

visit in class GrammarVisitor

Parameters:

m - The grammar module.

Returns:

Boolean.TRUE if the grammar has been modified, otherwise Boolean.FALSE.

visit

public Element visit(NonTerminal nt)

Visit the specified nonterminal.