java.lang.Object
- com.blackrook.expression.Expression

```
public class Expression
extends Object
```
An expression object for evaluating dynamic calculations. Expressions, at best, should do no memory allocations during evaluation - they can be called multiple times per gametic.

Author:

Matthew Tropiano

Field Summary

Fields
Modifier and Type	Field	Description
`static Expression`	`FALSE`	Expression: literal false.
`static Expression`	`FLOAT_0`	Expression: literal 0.0.
`static Expression`	`FLOAT_1`	Expression: literal 1.0.
`static Expression`	`INFINITY`	Expression: Infinity.
`static Expression`	`INTEGER_0`	Expression: literal 0.
`static Expression`	`INTEGER_1`	Expression: literal 1.
`static Expression`	`NAN`	Expression: NaN.
`static String`	`RETURN_VARIABLE`	Return variable name.
`static Expression`	`TRUE`	Expression: literal true.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`collapse()`	Collapses this expression.
`static Expression`	`create(boolean value)`	Creates an expression that is just one value.
`static Expression`	`create(double value)`	Creates an expression that is just one value.
`static Expression`	`create(long value)`	Creates an expression that is just one value.
`static Expression`	`create(ExpressionNode[] nodes)`	Creates an expression that is a full expression.
`static Expression`	`create(ExpressionValue value)`	Creates an expression that is just one value.
`boolean`	`equals(Expression other)`	Tests if two expressions are the same.
`boolean`	`equals(Object obj)`
`ExpressionValue`	`evaluate()`	Evaluates this expression.
`void`	`evaluate(ExpressionStack stack, ExpressionVariableContext context, ExpressionValue out)`	Evaluates this expression.
`void`	`evaluate(ExpressionValue out)`	Evaluates this expression.
`void`	`evaluate(ExpressionVariableContext context, ExpressionValue out)`	Evaluates this expression.
`String`	`getDigest()`	Gets the SHA-1 digest of this expression, in order to find duplicates.
`String`	`getDigest(boolean forceRecalc)`	Gets the SHA1 digest of this expression, in order to find duplicates.
`String`	`getSource()`	Gets the source code that was used to create this expression.
`Expression`	`intern()`	Internalizes an expression: adds this expression to an internal bank and returns it, or returns an existing reference for the same expression already stored.
`boolean`	`isCollapsible()`	Checks if this expression is collapsable.
`boolean`	`isValue()`	Checks if this is just a literal value (not complex).
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - RETURN_VARIABLE
```
public static final String RETURN_VARIABLE
```
    Return variable name.
    
    See Also:
    
    Constant Field Values
  - TRUE
```
public static final Expression TRUE
```
    Expression: literal true.
  - FALSE
```
public static final Expression FALSE
```
    Expression: literal false.
  - FLOAT_0
```
public static final Expression FLOAT_0
```
    Expression: literal 0.0.
  - FLOAT_1
```
public static final Expression FLOAT_1
```
    Expression: literal 1.0.
  - INTEGER_0
```
public static final Expression INTEGER_0
```
    Expression: literal 0.
  - INTEGER_1
```
public static final Expression INTEGER_1
```
    Expression: literal 1.
  - INFINITY
```
public static final Expression INFINITY
```
    Expression: Infinity.
  - NAN
```
public static final Expression NAN
```
    Expression: NaN.
- Method Detail
  - create
```
public static Expression create(boolean value)
```
    Creates an expression that is just one value.
    
    Parameters:
    
    value - the value.
    
    Returns:
    
    a new expression.
  - create
```
public static Expression create(long value)
```
    Creates an expression that is just one value.
    
    Parameters:
    
    value - the value.
    
    Returns:
    
    a new expression.
  - create
```
public static Expression create(double value)
```
    Creates an expression that is just one value.
    
    Parameters:
    
    value - the value.
    
    Returns:
    
    a new expression.
  - create
```
public static Expression create(ExpressionValue value)
```
    Creates an expression that is just one value.
    
    Parameters:
    
    value - the value.
    
    Returns:
    
    a new expression.
  - create
```
public static Expression create(ExpressionNode[] nodes)
```
    Creates an expression that is a full expression.
    
    Parameters:
    
    nodes - the list of expression nodes.
    
    Returns:
    
    a new expression.
  - evaluate
```
public void evaluate(ExpressionStack stack,
                     ExpressionVariableContext context,
                     ExpressionValue out)
```
    Evaluates this expression.
    
    Parameters:
    
    stack - the expression stack to use.
    
    context - the mutable variable context to use.
    
    out - the output value (returned value, top of stack, or literal value encapsulated).
  - evaluate
```
public void evaluate(ExpressionVariableContext context,
                     ExpressionValue out)
```
    Evaluates this expression. Creates a new stack.
    
    Parameters:
    
    context - the mutable variable context to use.
    
    out - the output value (returned value, top of stack, or literal value encapsulated).
  - evaluate
```
public void evaluate(ExpressionValue out)
```
    Evaluates this expression. Creates a new stack, and an empty context.
    
    Parameters:
    
    out - the output value (returned value, top of stack, or literal value encapsulated).
  - evaluate
```
public ExpressionValue evaluate()
```
    Evaluates this expression. Creates a new stack, an empty context, and a value to put the result in.
    
    Returns:
    
    the output value (returned value, top of stack, or literal value encapsulated).
  - collapse
```
public void collapse()
```
    Collapses this expression.
    
    See Also:
    
    evaluate(ExpressionValue), isCollapsible()
  - isCollapsible
```
public boolean isCollapsible()
```
    Checks if this expression is collapsable.
    
    Returns:
    
    true if so, false if not.
  - isValue
```
public boolean isValue()
```
    Checks if this is just a literal value (not complex).
    
    Returns:
    
    true if so, false if not.
  - getSource
```
public String getSource()
```
    Gets the source code that was used to create this expression.
    
    Returns:
    
    the source or null if not created from a string.
  - getDigest
```
public String getDigest()
```
    Gets the SHA-1 digest of this expression, in order to find duplicates. Within the Universe of all expressions, this digest should be sufficient enough to find equal expressions. Under the covers, this calculates the digest if it hasn't been calculated, yet. If it has, it returns the previously calculated digest.
    
    Returns:
    
    the SHA-1 digest.
  - getDigest
```
public String getDigest(boolean forceRecalc)
```
    Gets the SHA1 digest of this expression, in order to find duplicates.
    
    Parameters:
    
    forceRecalc - if true, forces a recalculation before return.
    
    Returns:
    
    a byte array of the digest.
    
    Throws:
    
    ExpressionException - if the digest could not be calculated for some reason.
  - intern
```
public Expression intern()
```
    Internalizes an expression: adds this expression to an internal bank and returns it, or returns an existing reference for the same expression already stored.
    
    Returns:
    
    this expression, or a reference to an equal one.
  - equals
```
public boolean equals(Object obj)
```
    Overrides:
    
    equals in class Object
  - equals
```
public boolean equals(Expression other)
```
    Tests if two expressions are the same. Only checks the digests - SHA1 hashes should be good enough.
    
    Parameters:
    
    other - the other expression.
    
    Returns:
    
    true if so, false if not.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class Expression

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

RETURN_VARIABLE

TRUE

FALSE

FLOAT_0

FLOAT_1

INTEGER_0

INTEGER_1

INFINITY

NAN

Method Detail

create

create

create

create

create

evaluate

evaluate

evaluate

evaluate

collapse

isCollapsible

isValue

getSource

getDigest

getDigest

intern

equals

equals

toString