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Refactored the calculator code for clarity. Added Jacoco line to prvent issues with the bigger Material class.
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src/main/java/world/bentobox/level/calculators/EquationEvaluator.java
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package world.bentobox.level.calculators; | ||
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import java.text.ParseException; | ||
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/** | ||
* @author tastybento | ||
*/ | ||
public class EquationEvaluator { | ||
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private static class Parser { | ||
private final String input; | ||
private int pos = -1; | ||
private int currentChar; | ||
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public Parser(String input) { | ||
this.input = input; | ||
moveToNextChar(); | ||
} | ||
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private void moveToNextChar() { | ||
currentChar = (++pos < input.length()) ? input.charAt(pos) : -1; | ||
} | ||
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private boolean tryToEat(int charToEat) { | ||
while (currentChar == ' ') | ||
moveToNextChar(); | ||
if (currentChar == charToEat) { | ||
moveToNextChar(); | ||
return true; | ||
} | ||
return false; | ||
} | ||
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public double evaluate() throws ParseException { | ||
double result = parseExpression(); | ||
if (pos < input.length()) { | ||
throw new ParseException("Unexpected character: " + (char) currentChar, pos); | ||
} | ||
return result; | ||
} | ||
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private double parseExpression() throws ParseException { | ||
double result = parseTerm(); | ||
while (true) { | ||
if (tryToEat('+')) | ||
result += parseTerm(); | ||
else if (tryToEat('-')) | ||
result -= parseTerm(); | ||
else | ||
return result; | ||
} | ||
} | ||
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private double parseFactor() throws ParseException { | ||
if (tryToEat('+')) | ||
return parseFactor(); // unary plus | ||
if (tryToEat('-')) | ||
return -parseFactor(); // unary minus | ||
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double x; | ||
int startPos = this.pos; | ||
if (tryToEat('(')) { // parentheses | ||
x = parseExpression(); | ||
tryToEat(')'); | ||
} else if ((currentChar >= '0' && currentChar <= '9') || currentChar == '.') { // numbers | ||
while ((currentChar >= '0' && currentChar <= '9') || currentChar == '.') | ||
moveToNextChar(); | ||
x = Double.parseDouble(input.substring(startPos, this.pos)); | ||
} else if (currentChar >= 'a' && currentChar <= 'z') { // functions | ||
while (currentChar >= 'a' && currentChar <= 'z') | ||
moveToNextChar(); | ||
String func = input.substring(startPos, this.pos); | ||
x = parseFactor(); | ||
switch (func) { | ||
case "sqrt": | ||
x = Math.sqrt(x); | ||
break; | ||
case "sin": | ||
x = Math.sin(Math.toRadians(x)); | ||
break; | ||
case "cos": | ||
x = Math.cos(Math.toRadians(x)); | ||
break; | ||
case "tan": | ||
x = Math.tan(Math.toRadians(x)); | ||
break; | ||
case "log": | ||
x = Math.log(x); | ||
break; | ||
default: | ||
throw new ParseException("Unknown function: " + func, startPos); | ||
} | ||
} else { | ||
throw new ParseException("Unexpected: " + (char) currentChar, startPos); | ||
} | ||
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if (tryToEat('^')) | ||
x = Math.pow(x, parseFactor()); // exponentiation | ||
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return x; | ||
} | ||
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private double parseTerm() throws ParseException { | ||
double x = parseFactor(); | ||
for (;;) { | ||
if (tryToEat('*')) | ||
x *= parseFactor(); // multiplication | ||
else if (tryToEat('/')) | ||
x /= parseFactor(); // division | ||
else | ||
return x; | ||
} | ||
} | ||
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} | ||
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public static double eval(final String equation) throws ParseException { | ||
return new Parser(equation).evaluate(); | ||
} | ||
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} |
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