X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=core%2Fsrc%2Fnet%2Fsf%2Fopenrocket%2Futil%2FExpressionParser.java;fp=core%2Fsrc%2Fnet%2Fsf%2Fopenrocket%2Futil%2FExpressionParser.java;h=d3a3fa62bcaf83a5b05c35f6f67eccd8e400a558;hb=9349577cdfdff682b2aabd6daa24fdc3a7449b58;hp=0000000000000000000000000000000000000000;hpb=30ba0a882f0c061176ba14dbf86d3d6fad096c02;p=debian%2Fopenrocket

diff --git a/core/src/net/sf/openrocket/util/ExpressionParser.java b/core/src/net/sf/openrocket/util/ExpressionParser.java
new file mode 100644
index 00000000..d3a3fa62
--- /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;
+	}
+}