Class ExpressionProgram

java.lang.Object
edu.hws.jcm.data.ExpressionProgram
All Implemented Interfaces:
Expression, Value, Serializable

public class ExpressionProgram extends 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.

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  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    If this is non-null, it is used as the print string for this expression in the toString() method.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
    static final int
    Code for a unary or binary operator or a standard function.
  • Constructor Summary

    Constructors
    Constructor
    Description
    Default constructor creates an initially empty program.
  • Method Summary

    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
    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, 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
    Checks whether the expression as a whole has any dependence on the variable x.
    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
    Run the ExprssionProgram and return the value that it computes.
    double
    Run the ExprssionProgram and return the value that it computes.
    If a source string has been saved, use it as the print string.
    void
    To save space, cut the arrays that holds the program data down to the actual amount of data that they contain.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
  • Field Details

    • PLUS

      public static final int PLUS
      Code for a unary or binary operator or a standard function.
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    • MINUS

      public static final int MINUS
      Code for a unary or binary operator or a standard function.
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    • TIMES

      public static final int TIMES
      Code for a unary or binary operator or a standard function.
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    • DIVIDE

      public static final int DIVIDE
      Code for a unary or binary operator or a standard function.
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    • POWER

      public static final int POWER
      Code for a unary or binary operator or a standard function.
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    • EQ

      public static final int EQ
      Code for a unary or binary operator or a standard function.
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    • NE

      public static final int NE
      Code for a unary or binary operator or a standard function.
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    • LT

      public static final int LT
      Code for a unary or binary operator or a standard function.
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    • GT

      public static final int GT
      Code for a unary or binary operator or a standard function.
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    • LE

      public static final int LE
      Code for a unary or binary operator or a standard function.
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    • GE

      public static final int GE
      Code for a unary or binary operator or a standard function.
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    • AND

      public static final int AND
      Code for a unary or binary operator or a standard function.
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    • OR

      public static final int OR
      Code for a unary or binary operator or a standard function.
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    • NOT

      public static final int NOT
      Code for a unary or binary operator or a standard function.
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    • UNARY_MINUS

      public static final int UNARY_MINUS
      Code for a unary or binary operator or a standard function.
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    • FACTORIAL

      public static final int FACTORIAL
      Code for a unary or binary operator or a standard function.
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    • SIN

      public static final int SIN
      Code for a unary or binary operator or a standard function.
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    • COS

      public static final int COS
      Code for a unary or binary operator or a standard function.
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    • TAN

      public static final int TAN
      Code for a unary or binary operator or a standard function.
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    • COT

      public static final int COT
      Code for a unary or binary operator or a standard function.
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    • SEC

      public static final int SEC
      Code for a unary or binary operator or a standard function.
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    • CSC

      public static final int CSC
      Code for a unary or binary operator or a standard function.
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    • ARCSIN

      public static final int ARCSIN
      Code for a unary or binary operator or a standard function.
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    • ARCCOS

      public static final int ARCCOS
      Code for a unary or binary operator or a standard function.
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    • ARCTAN

      public static final int ARCTAN
      Code for a unary or binary operator or a standard function.
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    • ABS

      public static final int ABS
      Code for a unary or binary operator or a standard function.
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    • SQRT

      public static final int SQRT
      Code for a unary or binary operator or a standard function.
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    • EXP

      public static final int EXP
      Code for a unary or binary operator or a standard function.
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    • LN

      public static final int LN
      Code for a unary or binary operator or a standard function.
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    • LOG2

      public static final int LOG2
      Code for a unary or binary operator or a standard function.
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    • LOG10

      public static final int LOG10
      Code for a unary or binary operator or a standard function.
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    • TRUNC

      public static final int TRUNC
      Code for a unary or binary operator or a standard function.
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    • ROUND

      public static final int ROUND
      Code for a unary or binary operator or a standard function.
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    • FLOOR

      public static final int FLOOR
      Code for a unary or binary operator or a standard function.
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    • CEILING

      public static final int CEILING
      Code for a unary or binary operator or a standard function.
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    • CUBERT

      public static final int CUBERT
      Code for a unary or binary operator or a standard function.
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    • sourceString

      public 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.)
  • Constructor Details

    • ExpressionProgram

      public ExpressionProgram()
      Default constructor creates an initially empty program.
  • Method Details

    • 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.
    • 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.
    • 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.
    • 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.
    • getVal

      public double getVal()
      Run the ExprssionProgram and return the value that it computes.
      Specified by:
      getVal in interface Value
    • 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 interface Expression
    • applyCommandCode

      protected double applyCommandCode(int code)
      Apply the stack operation represented by code (a number < 0) to the stack.
    • toString

      public 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 interface Expression
      Overrides:
      toString in class Object
    • appendOutputString

      public void appendOutputString(int index, 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.
    • 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 interface Expression
    • 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.
    • 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.
    • 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.
    • 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.
    • dependsOn

      public boolean dependsOn(Variable x)
      Checks whether the expression as a whole has any dependence on the variable x.
      Specified by:
      dependsOn in interface Expression