edu.davidson.numerics
Class Parser

java.lang.Object
  |
  +--edu.davidson.numerics.Parser

public final class Parser
extends java.lang.Object

The class Parser is a mathematical expression parser.

Example of code that uses this class:

 Parser parser = new Parser(1);    // creates parser with one variable
 parser.defineVariable(1,"x");     // lets the variable be 'x'
 parser.define("sin(x)/x");        // defines function: sin(x)/x
 parser.parse();                   // parses the function
 
 // calculates: sin(x)/x with x = -5.0 .. +5.0 in 20 steps
 // and prints the result to standard output.

 float result;
 for (i=-10; i <= 10; i++) {
   parser.setVariable(1,(float)i/2.0f);
   result = parser.evaluate();
   System.out.println(result);
 }
 


Field Summary
static int CODE_DAMAGED
          Code damaged.
static int COMMA_EXPECTED
          Comma expected.
static int EXPRESSION_EXPECTED
          Expression expected.
static int INVALID_OPERAND
          Invalid operand.
static int INVALID_OPERATOR
          Invalid operator.
static int NO_ERROR
          No error.
static int NO_FUNC_DEFINITION
          No function definition to parse.
static int OPERATOR_EXPECTED
          Operator expected.
static int PAREN_EXPECTED
          Parentheses expected.
static int PAREN_NOT_MATCH
          Parenthesis mismatch.
static int REF_NAME_EXPECTED
          Referenced name could not be found.
static int STACK_OVERFLOW
          Stack overflow.
static int SYNTAX_ERROR
          Syntax error.
static int TOO_MANY_CONSTS
          Too many constants.
static int UNCOMPILED_FUNCTION
          Attempt to evaluate an uncompiled function.
static int UNKNOWN_IDENTIFIER
          Unknown identifier.
 
Constructor Summary
Parser(int variablecount)
          The constructor of Parser.
 
Method Summary
 void define(java.lang.String definition)
          Defines a function.
 void defineVariable(int index, java.lang.String name)
          Sets the variable names.
 double evaluate()
          Evaluates compiled function.
 double evaluate(double x)
           
 double evaluate(double[] v)
           
 double evaluate(double x, double y)
           
 int getErrorCode()
          Gets error code of last operation.
 int getErrorPosition()
          Gets error position.
 java.lang.String getErrorString()
          Gets error string/message of last operation.
 java.lang.String getFunctionString()
          Gets function string of last operation.
 void parse()
          Parses defined function.
 void setVariable(int index, double value)
          Sets the variable value.
 void setVariable(java.lang.String name, double value)
          Sets the variable value.
static java.lang.String toErrorString(int errorcode)
          Converts error code to error string.
 void useDegree()
          Sets the angle unit to degree.
 void useRadian()
          Sets the angle unit to radian.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

NO_ERROR

public static final int NO_ERROR
No error.

SYNTAX_ERROR

public static final int SYNTAX_ERROR
Syntax error.

PAREN_EXPECTED

public static final int PAREN_EXPECTED
Parentheses expected.

UNCOMPILED_FUNCTION

public static final int UNCOMPILED_FUNCTION
Attempt to evaluate an uncompiled function.

EXPRESSION_EXPECTED

public static final int EXPRESSION_EXPECTED
Expression expected.

UNKNOWN_IDENTIFIER

public static final int UNKNOWN_IDENTIFIER
Unknown identifier.

OPERATOR_EXPECTED

public static final int OPERATOR_EXPECTED
Operator expected.

PAREN_NOT_MATCH

public static final int PAREN_NOT_MATCH
Parenthesis mismatch.

CODE_DAMAGED

public static final int CODE_DAMAGED
Code damaged.

STACK_OVERFLOW

public static final int STACK_OVERFLOW
Stack overflow.

TOO_MANY_CONSTS

public static final int TOO_MANY_CONSTS
Too many constants.

COMMA_EXPECTED

public static final int COMMA_EXPECTED
Comma expected.

INVALID_OPERAND

public static final int INVALID_OPERAND
Invalid operand.

INVALID_OPERATOR

public static final int INVALID_OPERATOR
Invalid operator.

NO_FUNC_DEFINITION

public static final int NO_FUNC_DEFINITION
No function definition to parse.

REF_NAME_EXPECTED

public static final int REF_NAME_EXPECTED
Referenced name could not be found.
Constructor Detail

Parser

public Parser(int variablecount)
The constructor of Parser.
Parameters:
variablecount - the number of variables
Method Detail

useRadian

public void useRadian()
Sets the angle unit to radian. Default upon construction.

useDegree

public void useDegree()
Sets the angle unit to degree.

defineVariable

public void defineVariable(int index,
                           java.lang.String name)
Sets the variable names. Nothing happens if variable index > number of variables.
Parameters:
index - the variable index (one based)
name - the variable name

setVariable

public void setVariable(int index,
                        double value)
Sets the variable value. The variable is accessed by index. Nothing happens if variable index > number of variables.
Parameters:
index - the variable index (one based)
value - the variable value

setVariable

public void setVariable(java.lang.String name,
                        double value)
Sets the variable value. The variable is accessed by name. Nothing happens if variable could not be found.
Parameters:
name - the variable name
value - the variable value

define

public void define(java.lang.String definition)
Defines a function. Current postfix code becomes invalid.
Parameters:
definition - the function definition

parse

public void parse()
Parses defined function.

evaluate

public double evaluate(double x,
                       double y)

evaluate

public double evaluate(double x)

evaluate

public double evaluate(double[] v)

evaluate

public double evaluate()
Evaluates compiled function.
Returns:
the result of the function

getErrorCode

public int getErrorCode()
Gets error code of last operation.
Returns:
the error code

getErrorString

public java.lang.String getErrorString()
Gets error string/message of last operation.
Returns:
the error string

getErrorPosition

public int getErrorPosition()
Gets error position. Valid only if error code != NO_ERROR
Returns:
error position (one based)

toErrorString

public static java.lang.String toErrorString(int errorcode)
Converts error code to error string.
Returns:
the error string

getFunctionString

public java.lang.String getFunctionString()
Gets function string of last operation.
Returns:
the function string

Copyright Wolfgang Christian

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