Merge commit '42b2e5ca519766e37ce6941ba4faecc9691cc403' into upstream

[debian/openrocket] / core / src / net / sf / openrocket / util / ExpressionParser.java

diff --git a/core/src/net/sf/openrocket/util/ExpressionParser.java b/core/src/net/sf/openrocket/util/ExpressionParser.java
new file mode 100644 (file)
index 0000000..d3a3fa6
--- /dev/null
+++ b/core/src/net/sf/openrocket/util/ExpressionParser.java
@@ -0,0 +1,67 @@
+package net.sf.openrocket.util;
+
+import java.text.DecimalFormatSymbols;
+
+import net.sf.openrocket.logging.LogHelper;
+import net.sf.openrocket.startup.Application;
+import de.congrace.exp4j.Calculable;
+import de.congrace.exp4j.ExpressionBuilder;
+
+public class ExpressionParser {
+       private static final LogHelper log = Application.getLogger();
+       
+       private static final char DECIMAL_SEPARATOR;
+       private static final char MINUS_SIGN;
+       static {
+               DecimalFormatSymbols symbols = DecimalFormatSymbols.getInstance();
+               DECIMAL_SEPARATOR = symbols.getDecimalSeparator();
+               MINUS_SIGN = symbols.getMinusSign();
+       }
+       
+       public double parse(String expression) throws InvalidExpressionException {
+               
+               String modified = null;
+               try {
+                       modified = modify(expression);
+                       ExpressionBuilder builder = new ExpressionBuilder(modified);
+                       Calculable calc = builder.build();
+                       double n = calc.calculate().getDoubleValue();
+                       log.debug("Evaluated expression '" + expression + "' (modified='" + modified + "') to " + n);
+                       return n;
+               } catch (Exception e) {
+                       log.warn("Unable to parse expression '" + expression + "' (modified='" + modified + "')", e);
+                       throw new InvalidExpressionException("Invalid expression: " + expression, e);
+               }
+       }
+       
+       private String modify(String exp) throws InvalidExpressionException {
+               
+               // Normalize digit equivalents, fraction sign, decimal separators and minus sign
+               char[] chars = exp.toCharArray();
+               for (int i = 0; i < chars.length; i++) {
+                       int value = Character.getNumericValue(chars[i]);
+                       if (value >= 0 && value < 10) {
+                               chars[i] = Character.toChars(48 + value)[0];
+                       }
+                       if (chars[i] == Chars.FRACTION) {
+                               chars[i] = '/';
+                       }
+                       if (chars[i] == DECIMAL_SEPARATOR || chars[i] == ',') {
+                               chars[i] = '.';
+                       }
+                       if (chars[i] == MINUS_SIGN) {
+                               chars[i] = '-';
+                       }
+               }
+               exp = String.copyValueOf(chars);
+               
+               // Replace fraction equivalents "1 3/4" with "(1+3/4)"
+               exp = exp.replaceAll("(?<![\\d.])(\\d+)\\s+(\\d+)\\s*/\\s*(\\d+)(?![\\d.])", "($1+$2/$3)");
+               
+               // Disallow spaces between numbers - default is to remove spaces!
+               if (exp.matches(".*[0-9.]\\s+[0-9.].*")) {
+                       throw new InvalidExpressionException("Expression contains excess space: " + exp);
+               }
+               return exp;
+       }
+}