Class ExpressionProgram
- java.lang.Object
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- edu.hws.jcm.data.ExpressionProgram
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- All Implemented Interfaces:
Expression
,Value
,java.io.Serializable
public class ExpressionProgram extends java.lang.Object implements Expression
An ExprssionProgram represents a mathematical expression such as "3" or "sin(x^2)", stored in the form of a program for a stack machine. The program consists of a sequence of commands that, when executed, will compute the value of the expression.Each command is encoded as an integer. There are three types of commands that can occur: (1) A negative integer must be one of the 36 constant values PLUS, MINUS,..., CUBERT. These constants represent unary and binary operators and standard functions. (2) An integer in the range 0 <= n < 0x3FFFFFFF encodes an operation of the form "push a constant onto the stack". The constant that is being pushed is encoded as an index in the array "constant", which is a private member of this class that holds all the constants that occur in this ExpressionProgram. (3) An integer >= 0x3FFFFFFF represents an ExpressionCommand object. When 0x3FFFFFFF is subtracted from the integer, the result is an index into the array "command", which is a private member of this class that holds all the ExpressionCommands that occur in this ExpressionProgram.
- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description static int
ABS
Code for a unary or binary operator or a standard function.static int
AND
Code for a unary or binary operator or a standard function.static int
ARCCOS
Code for a unary or binary operator or a standard function.static int
ARCSIN
Code for a unary or binary operator or a standard function.static int
ARCTAN
Code for a unary or binary operator or a standard function.static int
CEILING
Code for a unary or binary operator or a standard function.static int
COS
Code for a unary or binary operator or a standard function.static int
COT
Code for a unary or binary operator or a standard function.static int
CSC
Code for a unary or binary operator or a standard function.static int
CUBERT
Code for a unary or binary operator or a standard function.static int
DIVIDE
Code for a unary or binary operator or a standard function.static int
EQ
Code for a unary or binary operator or a standard function.static int
EXP
Code for a unary or binary operator or a standard function.static int
FACTORIAL
Code for a unary or binary operator or a standard function.static int
FLOOR
Code for a unary or binary operator or a standard function.static int
GE
Code for a unary or binary operator or a standard function.static int
GT
Code for a unary or binary operator or a standard function.static int
LE
Code for a unary or binary operator or a standard function.static int
LN
Code for a unary or binary operator or a standard function.static int
LOG10
Code for a unary or binary operator or a standard function.static int
LOG2
Code for a unary or binary operator or a standard function.static int
LT
Code for a unary or binary operator or a standard function.static int
MINUS
Code for a unary or binary operator or a standard function.static int
NE
Code for a unary or binary operator or a standard function.static int
NOT
Code for a unary or binary operator or a standard function.static int
OR
Code for a unary or binary operator or a standard function.static int
PLUS
Code for a unary or binary operator or a standard function.static int
POWER
Code for a unary or binary operator or a standard function.static int
ROUND
Code for a unary or binary operator or a standard function.static int
SEC
Code for a unary or binary operator or a standard function.static int
SIN
Code for a unary or binary operator or a standard function.java.lang.String
sourceString
If this is non-null, it is used as the print string for this expression in the toString() method.static int
SQRT
Code for a unary or binary operator or a standard function.static int
TAN
Code for a unary or binary operator or a standard function.static int
TIMES
Code for a unary or binary operator or a standard function.static int
TRUNC
Code for a unary or binary operator or a standard function.static int
UNARY_MINUS
Code for a unary or binary operator or a standard function.
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Constructor Summary
Constructors Constructor Description ExpressionProgram()
Default constructor creates an initially empty program.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addCommand(int code)
Add a command code to the program, where code is one of the opCode constants that are public final members of this class, from CUBERT to PLUS.void
addCommandObject(ExpressionCommand com)
Adds com as the next command in the program.void
addConstant(double d)
Add the number d as the next command in the program.void
appendOutputString(int index, java.lang.StringBuffer buffer)
Add a string representing part of the expression to the output buffer.protected double
applyCommandCode(int code)
Apply the stack operation represented by code (a number < 0) to the stack.void
compileDerivative(int index, ExpressionProgram deriv, Variable wrt)
The command at position index in the program represents a subexpression of the whole expression.void
copyExpression(int index, ExpressionProgram destination)
The command at position index in the program represents a subexpression of the whole expression.boolean
dependsOn(int index, Variable x)
The command at position index in the program represents a subexpression of the whole expression.boolean
dependsOn(Variable x)
Checks whether the expression as a whole has any dependence on the variable x.Expression
derivative(Variable wrt)
Compute the derivative of this expression with respect to the Variable wrt.int
extent(int index)
The command at position index in the program represents a subexpression of the whole expression.double
getVal()
Run the ExprssionProgram and return the value that it computes.double
getValueWithCases(Cases c)
Run the ExprssionProgram and return the value that it computes.java.lang.String
toString()
If a source string has been saved, use it as the print string.void
trim()
To save space, cut the arrays that holds the program data down to the actual amount of data that they contain.
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Field Detail
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PLUS
public static final int PLUS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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MINUS
public static final int MINUS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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TIMES
public static final int TIMES
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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DIVIDE
public static final int DIVIDE
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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POWER
public static final int POWER
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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EQ
public static final int EQ
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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NE
public static final int NE
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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LT
public static final int LT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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GT
public static final int GT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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LE
public static final int LE
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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GE
public static final int GE
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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AND
public static final int AND
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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OR
public static final int OR
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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NOT
public static final int NOT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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UNARY_MINUS
public static final int UNARY_MINUS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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FACTORIAL
public static final int FACTORIAL
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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SIN
public static final int SIN
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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COS
public static final int COS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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TAN
public static final int TAN
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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COT
public static final int COT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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SEC
public static final int SEC
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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CSC
public static final int CSC
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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ARCSIN
public static final int ARCSIN
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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ARCCOS
public static final int ARCCOS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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ARCTAN
public static final int ARCTAN
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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ABS
public static final int ABS
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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SQRT
public static final int SQRT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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EXP
public static final int EXP
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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LN
public static final int LN
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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LOG2
public static final int LOG2
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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LOG10
public static final int LOG10
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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TRUNC
public static final int TRUNC
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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ROUND
public static final int ROUND
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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FLOOR
public static final int FLOOR
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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CEILING
public static final int CEILING
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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CUBERT
public static final int CUBERT
Code for a unary or binary operator or a standard function.- See Also:
- Constant Field Values
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sourceString
public java.lang.String sourceString
If this is non-null, it is used as the print string for this expression in the toString() method. (When an expression is created by a Parser by parsing a string, the parse stores that string in this variable.)
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Method Detail
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addCommandObject
public void addCommandObject(ExpressionCommand com)
Adds com as the next command in the program. Among other things, for example, com can be a Variable or Constant. In that case, the meaning of the command is the stack operation "push (value of com)".- Parameters:
com
- added as next command in the program.
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addConstant
public void addConstant(double d)
Add the number d as the next command in the program. The meaning of this command is actually the stack operation "push d".- Parameters:
d
- added as next command in program.
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addCommand
public void addCommand(int code)
Add a command code to the program, where code is one of the opCode constants that are public final members of this class, from CUBERT to PLUS. Each code represents either a binary or unary operator or a standard function that operates on the stack by poping its argument(s) from the stack, perfroming the operation, and pushing the result back onto the stack.
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trim
public void trim()
To save space, cut the arrays that holds the program data down to the actual amount of data that they contain. This should be called after the complete program has been generated.
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getVal
public double getVal()
Run the ExprssionProgram and return the value that it computes.
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getValueWithCases
public double getValueWithCases(Cases c)
Run the ExprssionProgram and return the value that it computes. If the Cases object, c, is non-null, then information about "cases" is recorded in c. This information can be used to help detect possible "discontinuities" between two evaluations. See the Cases class for more information.- Specified by:
getValueWithCases
in interfaceExpression
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applyCommandCode
protected double applyCommandCode(int code)
Apply the stack operation represented by code (a number < 0) to the stack.
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toString
public java.lang.String toString()
If a source string has been saved, use it as the print string. (When a Parser creates an expression by parsing a string, it saves the source string in the ExpressionProgram.) Otherwise, construct the print string based on the commands in the program.- Specified by:
toString
in interfaceExpression
- Overrides:
toString
in classjava.lang.Object
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appendOutputString
public void appendOutputString(int index, java.lang.StringBuffer buffer)
Add a string representing part of the expression to the output buffer. You probably are only interested in this if you write a ParserExtension or ExpressionCommand. (The command at position index in the program represents a subexpression. It could be a constant or a variable, for example, which is complete subexpression in itself. Or it could be the final operator in a larger subexpression. In that case, the operands, which are located in lower positions in the program, are considered to be part of the expression. This routine appends a print string for the entire subexpression to the buffer. When this is called with index = progCt-1 (the last command in the program), it processes the entire program. Note that the hard part here is deciding when to put in parentheses. This is done based on the precedence of the operators. The result is not always pretty.
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derivative
public Expression derivative(Variable wrt)
Compute the derivative of this expression with respect to the Variable wrt. The value returned is actually an ExpressionProgram.- Specified by:
derivative
in interfaceExpression
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compileDerivative
public void compileDerivative(int index, ExpressionProgram deriv, Variable wrt)
The command at position index in the program represents a subexpression of the whole expression. This routine adds commands to deriv for computing the derivative of that subexpression with respect to the variable wrt. You probably are not interested in this unless you write a ParserExtension or an ExpressionCommand.
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extent
public int extent(int index)
The command at position index in the program represents a subexpression of the whole expression. This routine finds and returns the number of commands in the program that are part of that subexpression. That is, the subexpresssion occupies the part of the program between index - extent + 1 and index. You probably are not interested in this unless you write a ParserExtension or an ExpressionCommand.
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copyExpression
public void copyExpression(int index, ExpressionProgram destination)
The command at position index in the program represents a subexpression of the whole expression. This routine copies the commands for the entire subexpression to the destination program. You probably are not interested in this unless you write a ParserExtension or an ExpressionCommand.
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dependsOn
public boolean dependsOn(int index, Variable x)
The command at position index in the program represents a subexpression of the whole expression. If that subexpression includes some dependence on the variable x, then true is returned. If the subexpression is constant with respect to the variable x, then false is returned. You probably are not interested in this unless you write a ParserExtension or an ExpressionCommand.
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dependsOn
public boolean dependsOn(Variable x)
Checks whether the expression as a whole has any dependence on the variable x.- Specified by:
dependsOn
in interfaceExpression
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