Parser: hex float literals without decimal point (e.g. 0x0p0)

com.oracle.truffle.r.parser/src/com/oracle/truffle/r/parser/ParserGeneration.java

@@ -86,6 +86,7 @@ public class ParserGeneration {
         "remove deprecated calls to Source functions",
         "remove restricion on fixed number of digits in UTF codes",
         "support ? for help",
-        "support for hex float literals"
+        "support for hex float literals",
+        "support for hex float literals without decimal point: 0x0p0",
     };
 }

com.oracle.truffle.r.parser/src/com/oracle/truffle/r/parser/R.g

@@ -575,13 +575,13 @@ INTEGER
 COMPLEX
     : ('0'..'9')+ '.' ('0'..'9')* EXPONENT? 'i' { setText(getText().substring(0, getText().length()-1)); }
     | '.'? ('0'..'9')+ EXPONENT? 'i' { setText(getText().substring(0, getText().length()-1)); }
-    | '0x' HEX_DIGIT+ ('.' HEX_DIGIT* HEX_EXPONENT)? 'i' { setText(getText().substring(0, getText().length()-1)); }
+    | '0x' HEX_DIGIT+ ('.'? HEX_DIGIT* HEX_EXPONENT)? 'i' { setText(getText().substring(0, getText().length()-1)); }
     ;
 
 DOUBLE
     : ('0'..'9')+ '.' ('0'..'9')* EXPONENT?
     | '.'? ('0'..'9')+ EXPONENT?
-    | '0x' HEX_DIGIT+ ('.' HEX_DIGIT* HEX_EXPONENT)?
+    | '0x' HEX_DIGIT+ ('.'? HEX_DIGIT* HEX_EXPONENT)?
     ;
 
 DD : '..' ('0'..'9')+ ;

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/parser/TestParser.java

@@ -54,6 +54,8 @@ public class TestParser extends TestBase {
     @Test
     public void testDoubleLiterals() {
         assertEval("0x1.1p2");
+        assertEval("0x1p2");
+        assertEval("0x0p0");
         assertEval("0x1.aP2");
         assertEval("0xa.p2");
         assertEval("0xa.bp1i");