implement pictured numbers

include/fh_config.h

@@ -21,6 +21,7 @@
 
 #define HEAP_END      (HEAP_SIZE - WORDBUF_SIZE - INPUT_BUFFER_SIZE)
 #define WORDBUF_ADDR  HEAP_END
+#define WORDBUF_LASTCHAR_ADDR (WORDBUF_ADDR + WORDBUF_SIZE - 1)
 #define INPUTBUF_ADDR (HEAP_END + WORDBUF_SIZE)
 
 // SFR and magic addresses are "negative"

include/fh_error.h

@@ -28,6 +28,7 @@ enum fh_error {
   FH_ERR_ARITH,
   FH_ERR_SYNTAX,
   FH_ERR_NOT_APPLICABLE,
+  FH_ERR_PICTNUM_FULL,
   FH_ERR_MAX,
 };
 

include/fh_runtime.h

@@ -176,6 +176,9 @@ struct fh_thread_s {
   /** Address of the last dict word */
   uint32_t dict_last;
 
+  /** Pictured numeric output buffer write cursor (used for prepend) */
+  uint32_t pictnumptr;
+
   /** Input buffer parse position */
   uint32_t inputptr;
   /** Input buffer total content size */