1 files changed, 58 insertions, 0 deletions
diff --git a/dice-lang/src/bjc/dicelang/DoubleMatcher.java b/dice-lang/src/bjc/dicelang/DoubleMatcher.java
new file mode 100644
index 0000000..75df9c7
--- /dev/null
+++ b/dice-lang/src/bjc/dicelang/DoubleMatcher.java
@@ -0,0 +1,58 @@
+package bjc.dicelang;
+
+import java.util.regex.Pattern;
+
+/**
+ * Checks if a string would pass Double.parseDouble.
+ *
+ * Uses a regex from the javadoc for Double.valueOf()
+ */
+public class DoubleMatcher {
+	private static final String Digits =
+		"(\\p{Digit}+)";
+	private static final String HexDigits =
+		"(\\p{XDigit}+)";
+	
+	// an exponent is 'e' or 'E' followed by an optionally
+	// signed decimal integer.
+	private static final String Exp =
+		"[eE][+-]?" + Digits;
+
+	private static final String fpRegex    =
+		("[\\x00-\\x20]*" +  
+		 // Optional leading "whitespace"
+		 "[+-]?(" +         // Optional sign character
+		 "NaN|" +           // "NaN" string
+		 "Infinity|" +      // "Infinity" string
+
+		 // A decimal floating-point string representing a finite positive
+		 // number without a leading sign has at most five basic pieces:
+		 // Digits . Digits ExponentPart FloatTypeSuffix
+		 //
+		 // Since this method allows integer-only strings as input
+		 // in addition to strings of floating-point literals, the
+		 // two sub-patterns below are simplifications of the grammar
+		 // productions from section 3.10.2 of
+		 // The Java™ Language Specification.
+
+		 // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
+		 "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
+
+		 // . Digits ExponentPart_opt FloatTypeSuffix_opt
+		 "(\\.("+Digits+")("+Exp+")?)|"+
+
+		 // Hexadecimal strings
+		 "((" +
+		 // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
+		 "(0[xX]" + HexDigits + "(\\.)?)|" +
+
+		 // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
+		 "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
+
+		 ")[pP][+-]?" + Digits + "))" +
+		 "[fFdD]?))" +
+		 "[\\x00-\\x20]*");// Optional trailing "whitespace"
+
+	public static final Pattern floatingLiteral = Pattern.compile("\\A" + fpRegex + "\\Z");
+
+}