forth: add word ".X"

apps/forth/core.fs

@@ -50,7 +50,7 @@
 : / /MOD SWAP DROP ;
 : MOD /MOD DROP ;
 
-( Format decimals )
+( Format numbers )
 ( TODO FORGET this word )
 : PUSHDGTS
     999 SWAP        ( stop indicator )
@@ -73,3 +73,25 @@
     EMIT
     AGAIN
 ;
+
+: PUSHDGTS
+    999 SWAP        ( stop indicator )
+    DUP 0 = IF '0' EXIT THEN    ( 0 is a special case )
+    BEGIN
+    DUP 0 = IF DROP EXIT THEN
+    16 /MOD         ( r q )
+    SWAP            ( r q )
+    DUP 9 > IF 10 - 'a' +
+    ELSE '0' + THEN ( q d )
+    SWAP ( d q )
+    AGAIN
+;
+
+: .X              ( n -- )
+    ( For hex display, there are no negatives )
+    PUSHDGTS
+    BEGIN
+    DUP 'f' > IF DROP EXIT THEN ( stop indicator, we're done )
+    EMIT
+    AGAIN
+;

apps/forth/dictionary.txt

@@ -147,6 +147,8 @@ KEY input, however, is direct. Regardless of the input buffer's state, KEY will
 return the next typed key.
 
 .           n --            Print n in its decimal form
+.X          n --            Print n in its hexadecimal form. In hex, numbers
+                            are never considered negative. "-1 .X -> ffff"
 EMIT        c --            Spit char c to output stream
 IN>         -- a            Address of variable containing current pos in input
                             buffer.