com.ecfeed.core.export.Expression Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of ecfeed.junit Show documentation
Show all versions of ecfeed.junit Show documentation
An open library used to connect to the ecFeed service. It can be also used as a standalone testing tool. It is integrated with Junit5 and generates a stream of test cases using a selected algorithm (e.g. Cartesian, N-Wise). There are no limitations associated with the off-line version but the user cannot access the on-line computation servers and the model database.
The newest version!
/*******************************************************************************
*
* Copyright (c) 2016 ecFeed AS.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
*******************************************************************************/
package com.ecfeed.core.export;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Stack;
/**
* EvalEx - Java Expression Evaluator
*
* Introduction
* EvalEx is a handy expression evaluator for Java, that allows to evaluate simple mathematical and boolean expressions.
*
* Key Features:
*
* - Uses BigDecimal for calculation and result
* - Single class implementation, very compact
* - No dependencies to external libraries
* - Precision and rounding mode can be set
* - Supports variables
* - Standard boolean and mathematical operators
* - Standard basic mathematical and boolean functions
* - Custom functions and operators can be added at runtime
*
*
* Examples
*
* BigDecimal result = null;
*
* Expression expression = new Expression("1+1/3");
* result = expression.eval():
* expression.setPrecision(2);
* result = expression.eval():
*
* result = new Expression("(3.4 + -4.1)/2").eval();
*
* result = new Expression("SQRT(a^2 + b^2").with("a","2.4").and("b","9.253").eval();
*
* BigDecimal a = new BigDecimal("2.4");
* BigDecimal b = new BigDecimal("9.235");
* result = new Expression("SQRT(a^2 + b^2").with("a",a).and("b",b).eval();
*
* result = new Expression("2.4/PI").setPrecision(128).setRoundingMode(RoundingMode.UP).eval();
*
* result = new Expression("random() > 0.5").eval();
*
* result = new Expression("not(x<7 || sqrt(max(x,9)) <= 3))").with("x","22.9").eval();
*
*
* Supported Operators
*
* Mathematical Operators Operator Description + Additive operator - Subtraction operator * Multiplication operator / Division operator % Remainder operator (Modulo) ^ Power operator
*
*
* Boolean Operators* Operator Description = Equals == Equals != Not equals <> Not equals < Less than <= Less than or equal to > Greater than >= Greater than or equal to && Boolean and || Boolean or
* *Boolean operators result always in a BigDecimal value of 1 or 0 (zero). Any non-zero value is treated as a _true_ value. Boolean _not_ is implemented by a function.
*
* Supported Functions
*
* Function* Description NOT(expression) Boolean negation, 1 (means true) if the expression is not zero IF(condition,value_if_true,value_if_false) Returns one value if the condition evaluates to true or the other if it evaluates to false RANDOM() Produces a random number between 0 and 1 MIN(e1,e2) Returns the smaller of both expressions MAX(e1,e2) Returns the bigger of both expressions ABS(expression) Returns the absolute (non-negative) value of the expression ROUND(expression,precision) Rounds a value to a certain number of digits, uses the current rounding mode FLOOR(expression) Rounds the value down to the nearest integer CEILING(expression) Rounds the value up to the nearest integer LOG(expression) Returns the natural logarithm (base e) of an expression LOG10(expression) Returns the common logarithm (base 10) of an expression SQRT(expression) Returns the square root of an expression SIN(expression) Returns the trigonometric sine of an angle (in degrees) COS(expression) Returns the trigonometric cosine of an angle (in degrees) TAN(expression) Returns the trigonometric tangens of an angle (in degrees) ASIN(expression) Returns the angle of asin (in degrees) ACOS(expression) Returns the angle of acos (in degrees) ATAN(expression) Returns the angle of atan (in degrees) SINH(expression) Returns the hyperbolic sine of a value COSH(expression) Returns the hyperbolic cosine of a value TANH(expression) Returns the hyperbolic tangens of a value RAD(expression) Converts an angle measured in degrees to an approximately equivalent angle measured in radians DEG(expression) Converts an angle measured in radians to an approximately equivalent angle measured in degrees
* *Functions names are case insensitive.
*
* Supported Constants
*
* Constant Description PI The value of PI, exact to 100 digits TRUE The value one FALSE The value zero
*
* Add Custom Operators
*
* Custom operators can be added easily, simply create an instance of `Expression.Operator` and add it to the expression.
* Parameters are the operator string, its precedence and if it is left associative. The operators `eval()` method will be called with the BigDecimal values of the operands.
* All existing operators can also be overridden.
*
* For example, add an operator `x >> n`, that moves the decimal point of _x_ _n_ digits to the right:
*
*
* Expression e = new Expression("2.1234 >> 2");
*
* e.addOperator(e.new Operator(">>", 30, true) {
* {@literal @}Override
* public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
* return v1.movePointRight(v2.toBigInteger().intValue());
* }
* });
*
* e.eval(); // returns 212.34
*
*
* Add Custom Functions
*
* Adding custom functions is as easy as adding custom operators. Create an instance of `Expression.Function`and add it to the expression.
* Parameters are the function name and the count of required parameters. The functions `eval()` method will be called with a list of the BigDecimal parameters.
* All existing functions can also be overridden.
*
* For example, add a function `average(a,b,c)`, that will calculate the average value of a, b and c:
*
*
* Expression e = new Expression("2 * average(12,4,8)");
*
* e.addFunction(e.new Function("average", 3) {
* {@literal @}Override
* public BigDecimal eval(List parameters) {
* BigDecimal sum = parameters.get(0).add(parameters.get(1)).add(parameters.get(2));
* return sum.divide(new BigDecimal(3));
* }
* });
*
* e.eval(); // returns 16
*
* The software is licensed under the MIT Open Source license (see LICENSE file).
*
*
* - The *power of* operator (^) implementation was copied from [Stack Overflow](http://stackoverflow.com/questions/3579779/how-to-do-a-fractional-power-on-bigdecimal-in-java) Thanks to Gene Marin
* - The SQRT() function implementation was taken from the book [The Java Programmers Guide To numerical Computing](http://www.amazon.de/Java-Number-Cruncher-Programmers-Numerical/dp/0130460419) (Ronald Mak, 2002)
*
*
*@author Udo Klimaschewski (http://about.me/udo.klimaschewski)
*/
public class Expression {
/**
* Definition of PI as a constant, can be used in expressions as variable.
*/
public static final BigDecimal PI = new BigDecimal(
"3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679");
/**
* The {@link MathContext} to use for calculations.
*/
private MathContext mc = MathContext.DECIMAL32;
/**
* The original infix expression.
*/
private String expression = null;
/**
* The cached RPN (Reverse Polish Notation) of the expression.
*/
private List rpn = null;
/**
* All defined operators with name and implementation.
*/
private Map operators = new HashMap();
/**
* All defined functions with name and implementation.
*/
private Map functions = new HashMap();
/**
* All defined variables with name and value.
*/
private Map variables = new HashMap();
/**
* What character to use for decimal separators.
*/
private static final char decimalSeparator = '.';
/**
* What character to use for minus sign (negative values).
*/
private static final char minusSign = '-';
/**
* The expression evaluators exception class.
*/
public static class ExpressionException extends RuntimeException {
private static final long serialVersionUID = 1118142866870779047L;
public ExpressionException(String message) {
super(message);
}
}
/**
* Abstract definition of a supported expression function. A function is
* defined by a name, the number of parameters and the actual processing
* implementation.
*/
public abstract class Function {
/**
* Name of this function.
*/
private String name;
/**
* Number of parameters expected for this function.
*/
private int numParams;
/**
* Creates a new function with given name and parameter count.
*
* @param name
* The name of the function.
* @param numParams
* The number of parameters for this function.
*/
public Function(String name, int numParams) {
this.name = name.toUpperCase(Locale.ROOT);
this.numParams = numParams;
}
public String getName() {
return name;
}
public int getNumParams() {
return numParams;
}
/**
* Implementation for this function.
*
* @param parameters
* Parameters will be passed by the expression evaluator as a
* {@link List} of {@link BigDecimal} values.
* @return The function must return a new {@link BigDecimal} value as a
* computing result.
*/
public abstract BigDecimal eval(List parameters);
}
/**
* Abstract definition of a supported operator. An operator is defined by
* its name (pattern), precedence and if it is left- or right associative.
*/
public abstract class Operator {
/**
* This operators name (pattern).
*/
private String oper;
/**
* Operators precedence.
*/
private int precedence;
/**
* Operator is left associative.
*/
private boolean leftAssoc;
/**
* Creates a new operator.
*
* @param oper
* The operator name (pattern).
* @param precedence
* The operators precedence.
* @param leftAssoc
* true if the operator is left associative,
* else false.
*/
public Operator(String oper, int precedence, boolean leftAssoc) {
this.oper = oper;
this.precedence = precedence;
this.leftAssoc = leftAssoc;
}
public String getOper() {
return oper;
}
public int getPrecedence() {
return precedence;
}
public boolean isLeftAssoc() {
return leftAssoc;
}
/**
* Implementation for this operator.
*
* @param v1
* Operand 1.
* @param v2
* Operand 2.
* @return The result of the operation.
*/
public abstract BigDecimal eval(BigDecimal v1, BigDecimal v2);
}
/**
* Expression tokenizer that allows to iterate over a {@link String}
* expression token by token. Blank characters will be skipped.
*/
private class Tokenizer implements Iterator {
/**
* Actual position in expression string.
*/
private int pos = 0;
/**
* The original input expression.
*/
private String input;
/**
* The previous token or null if none.
*/
private String previousToken;
/**
* Creates a new tokenizer for an expression.
*
* @param input
* The expression string.
*/
public Tokenizer(String input) {
this.input = input.trim();
}
@Override
public boolean hasNext() {
return (pos < input.length());
}
/**
* Peek at the next character, without advancing the iterator.
*
* @return The next character or character 0, if at end of string.
*/
private char peekNextChar() {
if (pos < (input.length() - 1)) {
return input.charAt(pos + 1);
} else {
return 0;
}
}
@Override
public String next() {
StringBuilder token = new StringBuilder();
if (pos >= input.length()) {
return previousToken = null;
}
char ch = input.charAt(pos);
while (Character.isWhitespace(ch) && pos < input.length()) {
ch = input.charAt(++pos);
}
if (Character.isDigit(ch)) {
while ((Character.isDigit(ch) || ch == decimalSeparator)
&& (pos < input.length())) {
token.append(input.charAt(pos++));
ch = pos == input.length() ? 0 : input.charAt(pos);
}
} else if (ch == minusSign
&& Character.isDigit(peekNextChar())
&& ("(".equals(previousToken) || ",".equals(previousToken)
|| previousToken == null || operators
.containsKey(previousToken))) {
token.append(minusSign);
pos++;
token.append(next());
} else if (Character.isLetter(ch) || (ch == '_')) {
while ((Character.isLetter(ch) || Character.isDigit(ch) || (ch == '_')) && (pos < input.length())) {
token.append(input.charAt(pos++));
ch = pos == input.length() ? 0 : input.charAt(pos);
}
} else if (ch == '(' || ch == ')' || ch == ',') {
token.append(ch);
pos++;
} else {
while (!Character.isLetter(ch) && !Character.isDigit(ch) && ch != '_'
&& !Character.isWhitespace(ch) && ch != '('
&& ch != ')' && ch != ',' && (pos < input.length())) {
token.append(input.charAt(pos));
pos++;
ch = pos == input.length() ? 0 : input.charAt(pos);
if (ch == minusSign) {
break;
}
}
if (!operators.containsKey(token.toString())) {
throw new ExpressionException("Unknown operator '" + token
+ "' at position " + (pos - token.length() + 1));
}
}
return previousToken = token.toString();
}
@Override
public void remove() {
throw new ExpressionException("remove() not supported");
}
/**
* Get the actual character position in the string.
*
* @return The actual character position.
*/
public int getPos() {
return pos;
}
}
/**
* Creates a new expression instance from an expression string.
*
* @param expression
* The expression. E.g. "2.4*sin(3)/(2-4)" or
* "sin(y)>0 & max(z, 3)>3"
*/
public Expression(String expression) {
this.expression = expression;
addOperator(new Operator("+", 20, true) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.add(v2, mc);
}
});
addOperator(new Operator("-", 20, true) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.subtract(v2, mc);
}
});
addOperator(new Operator("*", 30, true) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.multiply(v2, mc);
}
});
addOperator(new Operator("/", 30, true) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.divide(v2, mc);
}
});
addOperator(new Operator("%", 30, true) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.remainder(v2, mc);
}
});
addOperator(new Operator("^", 40, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
/*-
* Thanks to Gene Marin:
* http://stackoverflow.com/questions/3579779/how-to-do-a-fractional-power-on-bigdecimal-in-java
*/
int signOf2 = v2.signum();
double dn1 = v1.doubleValue();
v2 = v2.multiply(new BigDecimal(signOf2)); // n2 is now positive
BigDecimal remainderOf2 = v2.remainder(BigDecimal.ONE);
BigDecimal n2IntPart = v2.subtract(remainderOf2);
BigDecimal intPow = v1.pow(n2IntPart.intValueExact(), mc);
BigDecimal doublePow = new BigDecimal(Math.pow(dn1,
remainderOf2.doubleValue()));
BigDecimal result = intPow.multiply(doublePow, mc);
if (signOf2 == -1) {
result = BigDecimal.ONE.divide(result, mc.getPrecision(),
RoundingMode.HALF_UP);
}
return result;
}
});
addOperator(new Operator("&&", 4, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
boolean b1 = !v1.equals(BigDecimal.ZERO);
boolean b2 = !v2.equals(BigDecimal.ZERO);
return b1 && b2 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator("||", 2, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
boolean b1 = !v1.equals(BigDecimal.ZERO);
boolean b2 = !v2.equals(BigDecimal.ZERO);
return b1 || b2 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator(">", 10, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) == 1 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator(">=", 10, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) >= 0 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator("<", 10, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) == -1 ? BigDecimal.ONE
: BigDecimal.ZERO;
}
});
addOperator(new Operator("<=", 10, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) <= 0 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator("=", 7, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) == 0 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator("==", 7, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return operators.get("=").eval(v1, v2);
}
});
addOperator(new Operator("!=", 7, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return v1.compareTo(v2) != 0 ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addOperator(new Operator("<>", 7, false) {
@Override
public BigDecimal eval(BigDecimal v1, BigDecimal v2) {
return operators.get("!=").eval(v1, v2);
}
});
addFunction(new Function("NOT", 1) {
@Override
public BigDecimal eval(List parameters) {
boolean zero = parameters.get(0).compareTo(BigDecimal.ZERO) == 0;
return zero ? BigDecimal.ONE : BigDecimal.ZERO;
}
});
addFunction(new Function("IF", 3) {
@Override
public BigDecimal eval(List parameters) {
boolean isTrue = !parameters.get(0).equals(BigDecimal.ZERO);
return isTrue ? parameters.get(1) : parameters.get(2);
}
});
addFunction(new Function("RANDOM", 0) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.random();
return new BigDecimal(d, mc);
}
});
addFunction(new Function("SIN", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.sin(Math.toRadians(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("COS", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.cos(Math.toRadians(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("TAN", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.tan(Math.toRadians(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("ASIN", 1) { // added by av
@Override
public BigDecimal eval(List parameters) {
double d = Math.toDegrees(Math.asin(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("ACOS", 1) { // added by av
@Override
public BigDecimal eval(List parameters) {
double d = Math.toDegrees(Math.acos(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("ATAN", 1) { // added by av
@Override
public BigDecimal eval(List parameters) {
double d = Math.toDegrees(Math.atan(parameters.get(0)
.doubleValue()));
return new BigDecimal(d, mc);
}
});
addFunction(new Function("SINH", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.sinh(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("COSH", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.cosh(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("TANH", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.tanh(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("RAD", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.toRadians(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("DEG", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.toDegrees(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("MAX", 2) {
@Override
public BigDecimal eval(List parameters) {
BigDecimal v1 = parameters.get(0);
BigDecimal v2 = parameters.get(1);
return v1.compareTo(v2) > 0 ? v1 : v2;
}
});
addFunction(new Function("MIN", 2) {
@Override
public BigDecimal eval(List parameters) {
BigDecimal v1 = parameters.get(0);
BigDecimal v2 = parameters.get(1);
return v1.compareTo(v2) < 0 ? v1 : v2;
}
});
addFunction(new Function("ABS", 1) {
@Override
public BigDecimal eval(List parameters) {
return parameters.get(0).abs(mc);
}
});
addFunction(new Function("LOG", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.log(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("LOG10", 1) {
@Override
public BigDecimal eval(List parameters) {
double d = Math.log10(parameters.get(0).doubleValue());
return new BigDecimal(d, mc);
}
});
addFunction(new Function("ROUND", 2) {
@Override
public BigDecimal eval(List parameters) {
BigDecimal toRound = parameters.get(0);
int precision = parameters.get(1).intValue();
return toRound.setScale(precision, mc.getRoundingMode());
}
});
addFunction(new Function("FLOOR", 1) {
@Override
public BigDecimal eval(List parameters) {
BigDecimal toRound = parameters.get(0);
return toRound.setScale(0, RoundingMode.FLOOR);
}
});
addFunction(new Function("CEILING", 1) {
@Override
public BigDecimal eval(List parameters) {
BigDecimal toRound = parameters.get(0);
return toRound.setScale(0, RoundingMode.CEILING);
}
});
addFunction(new Function("SQRT", 1) {
@Override
public BigDecimal eval(List parameters) {
/*
* From The Java Programmers Guide To numerical Computing
* (Ronald Mak, 2003)
*/
BigDecimal x = parameters.get(0);
if (x.compareTo(BigDecimal.ZERO) == 0) {
return new BigDecimal(0);
}
if (x.signum() < 0) {
throw new ExpressionException(
"Argument to SQRT() function must not be negative");
}
BigInteger n = x.movePointRight(mc.getPrecision() << 1)
.toBigInteger();
int bits = (n.bitLength() + 1) >> 1;
BigInteger ix = n.shiftRight(bits);
BigInteger ixPrev;
do {
ixPrev = ix;
ix = ix.add(n.divide(ix)).shiftRight(1);
// Give other threads a chance to work;
Thread.yield();
} while (ix.compareTo(ixPrev) != 0);
return new BigDecimal(ix, mc.getPrecision());
}
});
variables.put("PI", PI);
variables.put("TRUE", BigDecimal.ONE);
variables.put("FALSE", BigDecimal.ZERO);
}
/**
* Is the string a number?
*
* @param st
* The string.
* @return true, if the input string is a number.
*/
private boolean isNumber(String st) {
if (st.charAt(0) == minusSign && st.length() == 1)
return false;
for (char ch : st.toCharArray()) {
if (!Character.isDigit(ch) && ch != minusSign
&& ch != decimalSeparator)
return false;
}
return true;
}
/**
* Implementation of the Shunting Yard algorithm to transform an
* infix expression to a RPN expression.
*
* @param expression
* The input expression in infx.
* @return A RPN representation of the expression, with each token as a list
* member.
*/
private List shuntingYard(String expression) {
List outputQueue = new ArrayList();
Stack stack = new Stack();
Tokenizer tokenizer = new Tokenizer(expression);
String lastFunction = null;
String previousToken = null;
while (tokenizer.hasNext()) {
String token = tokenizer.next();
if (isNumber(token)) {
outputQueue.add(token);
} else if (variables.containsKey(token)) {
outputQueue.add(token);
} else if (functions.containsKey(token.toUpperCase(Locale.ROOT))) {
stack.push(token);
lastFunction = token;
} else if (Character.isLetter(token.charAt(0))) {
stack.push(token);
} else if (",".equals(token)) {
while (!stack.isEmpty() && !"(".equals(stack.peek())) {
outputQueue.add(stack.pop());
}
if (stack.isEmpty()) {
throw new ExpressionException("Parse error for function '"
+ lastFunction + "'");
}
} else if (operators.containsKey(token)) {
Operator o1 = operators.get(token);
String token2 = stack.isEmpty() ? null : stack.peek();
while (operators.containsKey(token2)
&& ((o1.isLeftAssoc() && o1.getPrecedence() <= operators
.get(token2).getPrecedence()) || (o1
.getPrecedence() < operators.get(token2)
.getPrecedence()))) {
outputQueue.add(stack.pop());
token2 = stack.isEmpty() ? null : stack.peek();
}
stack.push(token);
} else if ("(".equals(token)) {
if (previousToken != null) {
if (isNumber(previousToken)) {
throw new ExpressionException("Missing operator at character position " + tokenizer.getPos());
}
}
stack.push(token);
} else if (")".equals(token)) {
while (!stack.isEmpty() && !"(".equals(stack.peek())) {
outputQueue.add(stack.pop());
}
if (stack.isEmpty()) {
throw new RuntimeException("Mismatched parentheses");
}
stack.pop();
if (!stack.isEmpty()
&& functions.containsKey(stack.peek().toUpperCase(Locale.ROOT))) {
outputQueue.add(stack.pop());
}
}
previousToken = token;
}
while (!stack.isEmpty()) {
String element = stack.pop();
if ("(".equals(element) || ")".equals(element)) {
throw new RuntimeException("Mismatched parentheses");
}
if (!operators.containsKey(element)) {
throw new RuntimeException("Unknown operator or function: "
+ element);
}
outputQueue.add(element);
}
return outputQueue;
}
/**
* Evaluates the expression.
*
* @return The result of the expression.
*/
public BigDecimal eval() {
Stack stack = new Stack();
for (String token : getRPN()) {
if (operators.containsKey(token)) {
BigDecimal v1 = stack.pop();
BigDecimal v2 = stack.pop();
stack.push(operators.get(token).eval(v2, v1));
} else if (variables.containsKey(token)) {
stack.push(variables.get(token).round(mc));
} else if (functions.containsKey(token.toUpperCase(Locale.ROOT))) {
Function f = functions.get(token.toUpperCase(Locale.ROOT));
ArrayList p = new ArrayList(
f.getNumParams());
for (int i = 0; i < f.numParams; i++) {
p.add(0,stack.pop());
}
BigDecimal fResult = f.eval(p);
stack.push(fResult);
} else {
stack.push(new BigDecimal(token, mc));
}
}
return stack.pop().stripTrailingZeros();
}
/**
* Sets the precision for expression evaluation.
*
* @param precision
* The new precision.
*
* @return The expression, allows to chain methods.
*/
public Expression setPrecision(int precision) {
this.mc = new MathContext(precision);
return this;
}
/**
* Sets the rounding mode for expression evaluation.
*
* @param roundingMode
* The new rounding mode.
* @return The expression, allows to chain methods.
*/
public Expression setRoundingMode(RoundingMode roundingMode) {
this.mc = new MathContext(mc.getPrecision(), roundingMode);
return this;
}
/**
* Adds an operator to the list of supported operators.
*
* @param operator
* The operator to add.
* @return The previous operator with that name, or null if
* there was none.
*/
public Operator addOperator(Operator operator) {
return operators.put(operator.getOper(), operator);
}
/**
* Adds a function to the list of supported functions
*
* @param function
* The function to add.
* @return The previous operator with that name, or null if
* there was none.
*/
public Function addFunction(Function function) {
return functions.put(function.getName(), function);
}
/**
* Sets a variable value.
*
* @param variable
* The variable name.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression setVariable(String variable, BigDecimal value) {
variables.put(variable, value);
return this;
}
/**
* Sets a variable value.
*
* @param variable
* The variable to set.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression setVariable(String variable, String value) {
if (isNumber(value))
variables.put(variable, new BigDecimal(value));
else {
expression = expression.replaceAll("\\b" + variable + "\\b", "(" + value + ")");
rpn = null;
}
return this;
}
/**
* Sets a variable value.
*
* @param variable
* The variable to set.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression with(String variable, BigDecimal value) {
return setVariable(variable, value);
}
/**
* Sets a variable value.
*
* @param variable
* The variable to set.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression and(String variable, String value) {
return setVariable(variable, value);
}
/**
* Sets a variable value.
*
* @param variable
* The variable to set.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression and(String variable, BigDecimal value) {
return setVariable(variable, value);
}
/**
* Sets a variable value.
*
* @param variable
* The variable to set.
* @param value
* The variable value.
* @return The expression, allows to chain methods.
*/
public Expression with(String variable, String value) {
return setVariable(variable, value);
}
/**
* Get an iterator for this expression, allows iterating over an expression
* token by token.
*
* @return A new iterator instance for this expression.
*/
public Iterator getExpressionTokenizer() {
return new Tokenizer(this.expression);
}
/**
* Cached access to the RPN notation of this expression, ensures only one
* calculation of the RPN per expression instance. If no cached instance
* exists, a new one will be created and put to the cache.
*
* @return The cached RPN instance.
*/
private List getRPN() {
if (rpn == null) {
rpn = shuntingYard(this.expression);
}
return rpn;
}
/**
* Get a string representation of the RPN (Reverse Polish Notation) for this
* expression.
*
* @return A string with the RPN representation for this expression.
*/
public String toRPN() {
StringBuilder result = new StringBuilder();
for (String st : getRPN()) {
if (result.length() != 0)
result.append(" ");
result.append(st);
}
return result.toString();
}
} © 2015 - 2025 Weber Informatics LLC | Privacy Policy