net.sf.transjvm
Class Expression

java.lang.Object
  net.sf.transjvm.Expression

Direct Known Subclasses:

Variable

public abstract class Expression
extends java.lang.Object

This class represents expressions. Each expression generates code which leaves a single value at the top of the stack.

Author:

Mark Shannon

See Also:

ConstructorID.newInstance(), MethodID.call(Expression object), Variable.assign(Expression value)

Field Summary

static Expression	FALSE Expression representing the constant false.
static Expression	NULL Expression representing the constant null.
static Expression	ONE Expression representing the int constant 1 (one).
static Expression	TRUE Expression representing the constant true.
static Expression	ZERO Expression representing the int constant 0 (zero).

Constructor Summary

protected

Expression(TypeID type)

Method Summary

abstract java.lang.Object	accept(ExpressionVisitor visitor)
Expression	bitwise(Operator.Math op, Expression right) Deprecated. Use math(op, right) instead.
Expression	bitwiseNot() Returns an expression representing the bitwise not of this Expression.
Statement	branch(boolean branch, Label target) Returns a conditional branch statement.
void	branch(boolean onTrue, Label target, InstructionStream stream) Branches to target if this Expression evaluates to onTrue.
void	branch(boolean onTrue, Label target, InstructionStream stream, int depth)
Expression	cast(TypeID cls) Casts this expression to type cls.
Expression	compare(Operator.Compare op, Expression right) Returns an expression representing the comparison this op right.
Expression	conditional(Expression ifTrue, Expression ifFalse) Returns an Expression which evaluates to either ifTrue or ifFalse.
static Expression	constant(double value) Returns an Expression representing a double constant.
static Expression	constant(float value) Returns an Expression representing the constant value.
static Expression	constant(int value) Returns an Expression representing an int constant.
static Expression	constant(long value) Returns an Expression representing a long constant.
static Expression	constant(java.lang.String value) Returns an Expression representing a string constant
Expression	convert(TypeID to) Converts this expression to type to .
static Expression	emptyArray(TypeID componentType, Expression size)
abstract void	eval(InstructionStream stream, int depth) Writes the code to stream necessary for the evaluation of this Expression.
static Expression	filledArray(TypeID memberType, Expression... items) Returns an expression for an array of type memberType, containing items.
TypeID	getType() Gets the type of this Expression
Variable	index(Expression index) Returns a variable for an indexed array member.
Expression	isInstanceOf(TypeID type) Returns an expression representing this instanceof type.
Expression	length() Returns a Expression for the length of this array.
Expression	logicalNot() Returns an expression representing the logical converse of this Expression.
Expression	math(Operator.Math op, Expression right) Returns an Expression representing this op right.
Expression	negate() Returns an expression representing the negative of this Expression.
Expression	not() Deprecated. Use logicalNot() or bitwiseNot() instead. Acts as logicalNot() if this expression is boolean, bitwiseNot() otherwise.
Expression	shortCut(Operator.Boolean op, Expression right) Returns an Expression representing this op right.
Statement	toStm() Returns a statement which evaluates this Expression, then discards the result.

Methods inherited from class java.lang.Object

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

Field Detail

TRUE

public static Expression TRUE

Expression representing the constant true.

FALSE

public static Expression FALSE

Expression representing the constant false.

NULL

public static final Expression NULL

Expression representing the constant null.

ZERO

public static final Expression ZERO

Expression representing the int constant 0 (zero).

ONE

public static final Expression ONE

Expression representing the int constant 1 (one).

Constructor Detail

Expression

protected Expression(TypeID type)

Method Detail

accept

public abstract java.lang.Object accept(ExpressionVisitor visitor)

eval

public abstract void eval(InstructionStream stream,
                          int depth)

Writes the code to stream necessary for the evaluation of this Expression. Must also ensures that sufficient stack space is allocated if the stack depth during evaluation exceeds the final stack depth.

Parameters:

depth - The stack depth before evaluation

stream - Description of the Parameter

See Also:

InstructionStream.stackDepth(int depth)

getType

public final TypeID getType()

Gets the type of this Expression

Returns:

The type of this Expression

branch

public final void branch(boolean onTrue,
                         Label target,
                         InstructionStream stream)

Branches to target if this Expression evaluates to onTrue.

Parameters:

onTrue - If true, branches when thisExpression evaluates to true.

target - Target of the jump.

stream - The instruction stream.

branch

public Statement branch(boolean branch,
                        Label target)

Returns a conditional branch statement.

Parameters:

branch - If this expression evaluates to branch jump to target.

target - The target Label.

Returns:

A conditional branch statement.

Throws:

java.lang.IllegalStateException - if type is not boolean.

branch

public void branch(boolean onTrue,
                   Label target,
                   InstructionStream stream,
                   int depth)

toStm

public Statement toStm()

Returns a statement which evaluates this Expression, then discards the result.

Returns:

A statement which evaluates this Expression.

constant

public static Expression constant(int value)

Returns an Expression representing an int constant.

Parameters:

value - An int constant

Returns:

An Expression representing the constant value

constant

public static Expression constant(long value)

Returns an Expression representing a long constant.

Parameters:

value - A long constant

Returns:

An Expression representing the constant value

constant

public static Expression constant(double value)

Returns an Expression representing a double constant.

Parameters:

value - A double constant

Returns:

An Expression representing the constant value

constant

public static Expression constant(float value)

Returns an Expression representing the constant value.

Parameters:

value - A float constant

Returns:

An Expression representing the constant value

constant

public static Expression constant(java.lang.String value)

Returns an Expression representing a string constant

Parameters:

value - A String constant

Returns:

An Expression representing the constant value

logicalNot

public Expression logicalNot()

Returns an expression representing the logical converse of this Expression.

Returns:

An expression representing (bitwise) not this Expression.

not

@Deprecated
public final Expression not()

Deprecated. Use logicalNot() or bitwiseNot() instead. Acts as logicalNot() if this expression is boolean, bitwiseNot() otherwise.

bitwiseNot

public Expression bitwiseNot()

Returns an expression representing the bitwise not of this Expression.

Returns:

An expression representing (bitwise) not this Expression.

negate

public final Expression negate()

Returns an expression representing the negative of this Expression.

Returns:

An expression representing the negative of this Expression.

conditional

public final Expression conditional(Expression ifTrue,
                                    Expression ifFalse)

Returns an Expression which evaluates to either ifTrue or ifFalse. Both ifTrue and ifFalse should be of the same type. This expression should be boolean.

Parameters:

ifTrue - The true Expression

ifFalse - The false Expression

Returns:

The resulting Expression, which is ifTrue if this is true, otherwise ifFalse.

shortCut

public Expression shortCut(Operator.Boolean op,
                           Expression right)

Returns an Expression representing this op right. Both this and right should be booleans. Short-cut evaluation is used, ie. right is only evaluated if required to produce the result. If you require right to be evaluated, use binary(BinaryOperator op, Expression right).

Parameters:

op - The operator

right - The right hand Expression

Returns:

The resulting Expression

math

public Expression math(Operator.Math op,
                       Expression right)

Returns an Expression representing this op right.

Parameters:

op - The operator

right - The right hand Expression

Returns:

The resulting Expression

bitwise

@Deprecated
public Expression bitwise(Operator.Math op,
                                     Expression right)

Deprecated. Use math(op, right) instead.

Returns an Expression representing this op right.

Parameters:

op - The operator

right - The right hand Expression

Returns:

The resulting Expression

cast

public Expression cast(TypeID cls)

Casts this expression to type cls.

Parameters:

cls - TypeID to be cast to

Returns:

This expression cast to cls.

Throws:

java.lang.IllegalArgumentException - if cls is primitive

convert

public Expression convert(TypeID to)

Converts this expression to type to . Both this expression and to must be numeric.

Parameters:

to - The type converted to.

Returns:

An expression of type to .

index

public Variable index(Expression index)

Returns a variable for an indexed array member.

Parameters:

index - The index of the array member, must be of type INT32. Also getType().isArray() must be true, ie. This expression must represent an array.

emptyArray

public static Expression emptyArray(TypeID componentType,
                                    Expression size)

Parameters:

componentType - The type of the components of the array.

size - The size of the new array, must be of type Int32

Returns:

An expression for the new array.

filledArray

public static Expression filledArray(TypeID memberType,
                                     Expression... items)

Returns an expression for an array of type memberType, containing items. The new array will have a length equal to items.

Parameters:

memberType - The type of the array items. ie array has type memberType[].

items - The values to fill the array.

Returns:

An expression for an array of type memberType, containing items.

compare

public Expression compare(Operator.Compare op,
                          Expression right)

Returns an expression representing the comparison this op right.

Parameters:

op - The operator.

right - The rhs of the comparison.

Returns:

A boolean expression representing this op right.

isInstanceOf

public Expression isInstanceOf(TypeID type)

Returns an expression representing this instanceof type.

Parameters:

type - The type.

Returns:

A boolean expression representing this instanceof type.

Throws:

java.lang.IllegalArgumentException - if type is primitive.

length

public Expression length()

Returns a Expression for the length of this array. This Expression must be an array.

Returns:

An expression of type INT32 representing the length of this array.