git.gag.com Git - debian/openrocket/blob - core/src/net/sf/openrocket/util/ExpressionParser.java

   1 package net.sf.openrocket.util;
   2
   3 import java.text.DecimalFormatSymbols;
   4
   5 import net.sf.openrocket.logging.LogHelper;
   6 import net.sf.openrocket.startup.Application;
   7 import de.congrace.exp4j.Calculable;
   8 import de.congrace.exp4j.ExpressionBuilder;
   9
  10 public class ExpressionParser {
  11         private static final LogHelper log = Application.getLogger();
  12
  13         private static final char DECIMAL_SEPARATOR;
  14         private static final char MINUS_SIGN;
  15         static {
  16                 DecimalFormatSymbols symbols = DecimalFormatSymbols.getInstance();
  17                 DECIMAL_SEPARATOR = symbols.getDecimalSeparator();
  18                 MINUS_SIGN = symbols.getMinusSign();
  19         }
  20
  21         public double parse(String expression) throws InvalidExpressionException {
  22
  23                 String modified = null;
  24                 try {
  25                         modified = modify(expression);
  26                         ExpressionBuilder builder = new ExpressionBuilder(modified);
  27                         Calculable calc = builder.build();
  28                         double n = calc.calculate();
  29                         log.debug("Evaluated expression '" + expression + "' (modified='" + modified + "') to " + n);
  30                         return n;
  31                 } catch (Exception e) {
  32                         log.warn("Unable to parse expression '" + expression + "' (modified='" + modified + "')", e);
  33                         throw new InvalidExpressionException("Invalid expression: " + expression, e);
  34                 }
  35         }
  36
  37         private String modify(String exp) throws InvalidExpressionException {
  38
  39                 // Normalize digit equivalents, fraction sign, decimal separators and minus sign
  40                 char[] chars = exp.toCharArray();
  41                 for (int i = 0; i < chars.length; i++) {
  42                         int value = Character.getNumericValue(chars[i]);
  43                         if (value >= 0 && value < 10) {
  44                                 chars[i] = Character.toChars(48 + value)[0];
  45                         }
  46                         if (chars[i] == Chars.FRACTION) {
  47                                 chars[i] = '/';
  48                         }
  49                         if (chars[i] == DECIMAL_SEPARATOR || chars[i] == ',') {
  50                                 chars[i] = '.';
  51                         }
  52                         if (chars[i] == MINUS_SIGN) {
  53                                 chars[i] = '-';
  54                         }
  55                 }
  56                 exp = String.copyValueOf(chars);
  57
  58                 // Replace fraction equivalents "1 3/4" with "(1+3/4)"
  59                 exp = exp.replaceAll("(?<![\\d.])(\\d+)\\s+(\\d+)\\s*/\\s*(\\d+)(?![\\d.])", "($1+$2/$3)");
  60
  61                 // Disallow spaces between numbers - default is to remove spaces!
  62                 if (exp.matches(".*[0-9.]\\s+[0-9.].*")) {
  63                         throw new InvalidExpressionException("Expression contains excess space: " + exp);
  64                 }
  65                 return exp;
  66         }
  67 }