Well, that's a hack. But it works.

HISTORY.markdown

@@ -5,6 +5,7 @@ History of SixtyPical
 -------
 
 *   Added `byte table` type locations and indexed addressing (`+ x`, `+ y`).
+*   Integer literals may be given in hexadecimal.
 
 0.4
 ---

README.markdown

@@ -33,7 +33,6 @@ TODO
 
 For 0.5:
 
-*   hexadecimal literals.
 *   source code comments.
 
 For 0.6:

src/sixtypical/parser.py

@@ -37,6 +37,11 @@ class Scanner(object):
             return
         if self.scan_pattern(r'\d+', 'integer literal'):
             return
+        if self.scan_pattern(r'\$([0-9a-fA-F]+)', 'integer literal',
+                             token_group=2, rest_group=3):
+            # ecch
+            self.token = str(eval('0x' + self.token))
+            return
         if self.scan_pattern(r'\"(.*?)\"', 'string literal',
                              token_group=2, rest_group=3):
             return

tests/SixtyPical Execution.md

@@ -61,7 +61,7 @@ Add honours carry.
     = z: 1
 
     | routine main {
-    |     ld a, 255
+    |     ld a, $ff
     |     st off, c
     |     add a, 1
     |   }

tests/SixtyPical Syntax.md

@@ -19,7 +19,15 @@ Rudimentary program.
     | }
     = ok
 
-Syntax error
+Hex literals.
+
+    | routine main {
+    |     ld a, $ff
+    |     add a, $01
+    | }
+    = ok
+
+Syntax error.
 
     | routine foo (
     |     ld a, 0
@@ -27,7 +35,7 @@ Syntax error
     | )
     ? SyntaxError
 
-Another syntax error
+Another syntax error.
 
     | byte glee
     | {