fix number reading

NPException · Nov 12, 2018 · 06314d6 · 06314d6
1 parent 62ed37f
commit 06314d6
Showing 1 changed file with 11 additions and 1 deletion.
diff --git a/src/main/java/de/npecomplete/mc/testproject/lisp/util/LispTokenizer.java b/src/main/java/de/npecomplete/mc/testproject/lisp/util/LispTokenizer.java
@@ -130,7 +130,7 @@ private Token computeNext() {
 			return Token.NULL;
 		}
 
-		if (Character.isDigit(value.charAt(0))) {
+		if (isNumberCandidate(value)) {
 			if (value.chars().allMatch(Character::isDigit)) {
 				try {
 					long number = Long.parseLong(value);
@@ -150,6 +150,16 @@ private Token computeNext() {
 		return new Token(Type.SYMBOL, value);
 	}
 
+	private static boolean isNumberCandidate(String value) {
+		char first = value.charAt(0);
+		if (Character.isDigit(first)) {
+			return true;
+		}
+		char second = value.length() > 1 ? value.charAt(1) : '?';
+		return (first == '-' || first == '+')
+				&& Character.isDigit(second);
+	}
+
 	private String finishToken(int chr) {
 		StringBuilder sb = new StringBuilder();
 		sb.appendCodePoint(chr);