antlraux.context.asts
Class ExpressionAST

java.lang.Object
  |
  +--antlr.BaseAST
        |
        +--antlr.CommonAST
              |
              +--antlraux.util.LexInfoAST
                    |
                    +--antlraux.context.asts.TypeAST
                          |
                          +--antlraux.context.asts.ExpressionAST

All Implemented Interfaces:

antlr.collections.AST, LexInfo, java.io.Serializable

public class ExpressionAST

extends TypeAST

This class can be used to modelize the AST of an expression. It features an expression type (a Type), an RValue, LValue, and value.

Warning: TypeAST, ExpressionAST and ScopeAST copy first child and sibling with their only constructor. See their constructor's comments for details.

See Also:

Serialized Form

Field Summary

protected java.lang.Object	EValue This is a calculated value.
protected boolean	LValue An expression with left value set to true can be put on the left sign of an assignation; otherwise, they can't.
protected boolean	RValue An expression with no Rvalue cannot be used on the right side of an assignation, because they are not "readable".
protected static boolean	verboseStringConversion

Fields inherited from class antlr.BaseAST

down, right

Fields inherited from interface antlraux.util.LexInfo

DEFAULT_COLUMN, DEFAULT_FILENAME, DEFAULT_LINE

Constructor Summary

ExpressionAST()

ExpressionAST(antlr.collections.AST other)
This constructor copies the first child and next sibling of other using the initialize(AST) method

Method Summary

java.lang.Object	getEValue()
boolean	getLValue()
boolean	getRValue()
void	initialize(antlr.collections.AST ast) Warning: this implementation of initialize copies the first child and next sibling of ast.
void	setEValue(java.lang.Object o)
void	setLValue(boolean b)
void	setRValue(boolean b)
static void	setVerboseStringConversion(boolean b) If set to true, this adds some additional information to the string generated by toString() (shows the AST's type, RValue, LValue and EValue)
java.lang.String	toString() Returns a String representing the information in the root of the node.

Methods inherited from class antlraux.context.asts.TypeAST

getExpType, setExpType

Methods inherited from class antlraux.util.LexInfoAST

addChildLeft, addChildLeftWithSiblings, addSibling, copyLexInfo, getColumn, getFilename, getLastChild, getLastSibling, getLexInfoString, getLine, getPrevChild, initialize, replaceChild, replaceChildWithSiblings, setColumn, setFilename, setLine, tabulate, toStringList, toStringList, toStringTree

Methods inherited from class antlr.CommonAST

getText, getType, initialize, setText, setType

Methods inherited from class antlr.BaseAST

addChild, decode, encode, equals, equalsList, equalsListPartial, equalsTree, equalsTreePartial, findAll, findAllPartial, getFirstChild, getNextSibling, getNumberOfChildren, removeChildren, setFirstChild, setNextSibling, setVerboseStringConversion, xmlSerialize, xmlSerializeNode, xmlSerializeRootClose, xmlSerializeRootOpen

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

LValue

protected boolean LValue

An expression with left value set to true can be put on the left sign of an assignation; otherwise, they can't. An example of expression with LValue is a variable:

 a = 3; 

An expression without LValue could be a literal or an addition:

 "Hello"="world"; // Incorrect; "Hello" does not have LValue
 a+b = c;         // Incorrect: a+b has no LValue
 

Keep in mind that these are examples. Of course your languajes could consider having literals with lvalues...

RValue

protected boolean RValue

An expression with no Rvalue cannot be used on the right side of an assignation, because they are not "readable". The typical example is an invocation to a method that returns nothing:

 void voidFunction() {...}
 
 ...
 
 int a = voidFunction(); // Incorrect; Rvalue required
 

Of course this is an example. Some languajes might find useful setting LValue to true in this kind of function calls (thus recuperating a void value).

EValue

protected java.lang.Object EValue

This is a calculated value. Some initializations must be calculated in compile-time; for example static attribute initialization:

 class MyDumbClass{
   public int staticInt = 1+5+6;
 }
 

The value for literal "1" will be the integer 1, the value for literal "5" will be the integer 5, and the value for "6" will the the integer 6. This way, "1+5+6" can be evaluated in compile time (and set to 12).

Other use for this field is in iterpreters: The only way of calculating values is having them dynamically stored in the ASTs.

verboseStringConversion

protected static boolean verboseStringConversion

Constructor Detail

ExpressionAST

public ExpressionAST()

ExpressionAST

public ExpressionAST(antlr.collections.AST other)

This constructor copies the first child and next sibling of other using the initialize(AST) method

Method Detail

setLValue

public void setLValue(boolean b)

setRValue

public void setRValue(boolean b)

setEValue

public void setEValue(java.lang.Object o)

getLValue

public boolean getLValue()

getRValue

public boolean getRValue()

getEValue

public java.lang.Object getEValue()

initialize

public void initialize(antlr.collections.AST ast)

Warning: this implementation of initialize copies the first child and next sibling of ast.

Specified by:

initialize in interface antlr.collections.AST

Overrides:

initialize in class TypeAST

Parameters:

ast - The AST whose information is to be copied

setVerboseStringConversion

public static void setVerboseStringConversion(boolean b)

If set to true, this adds some additional information to the string generated by toString() (shows the AST's type, RValue, LValue and EValue)

toString

public java.lang.String toString()

Description copied from class: LexInfoAST

Returns a String representing the information in the root of the node. If LexInfoAST.setVerboseStringConversion(boolean) has been set to true, it adds the lex information of the AST (using LexInfoAST.getLexInfoString())

Specified by:

toString in interface antlr.collections.AST

Overrides:

toString in class TypeAST