Allow label names to begin with a valid register name (e.g., R1_INIT)

Resolves #3

hera/parser.py

@@ -44,6 +44,10 @@ def value(self, matches):
             ntkn.end_line = otkn.end_line
             ntkn.end_column = otkn.end_column
             return ntkn
+        elif matches[0].type == "SYMBOL":
+            if matches[0][0] in "rR" and matches[0][1:].isdigit():
+                matches[0].type = "REGISTER"
+            return matches[0]
         else:
             return matches[0]
 
@@ -65,10 +69,9 @@ def value(self, matches):
 
     _arglist: ( value "," )* value
 
-    value: DECIMAL | HEX | OCTAL | BINARY | REGISTER | SYMBOL | STRING
+    value: DECIMAL | HEX | OCTAL | BINARY | SYMBOL | STRING
 
-    REGISTER.3: /[rR][0-9]+/
-    SYMBOL.2: /[A-Za-z_][A-Za-z0-9_]*/
+    SYMBOL: /[A-Za-z_][A-Za-z0-9_]*/
     DECIMAL: /-?[0-9]+/
     HEX: /-?0x[0-9a-fA-F]+/
     // TODO: How should I handle zero-prefixed numbers, which the HERA-C

test/test_parser.py

@@ -71,6 +71,10 @@ def test_parse_negative_octal_number():
     assert parse("SETLO(R3, -0o173)") == [Op("SETLO", ["R3", -123])]
 
 
+def test_parse_label_starting_with_register_name():
+    assert parse("LABEL(R1_INIT)") == [Op("LABEL", ["R1_INIT"])]
+
+
 def test_parse_single_line_comment():
     assert parse("SETLO(R1, 0)  // R1 <- 0") == [Op("SETLO", ["R1", 0])]