+
+(16) We now know the offset of the current field relative to the
+ whole match. This may allow more efficient aligned versions
+ of functions to be called (at compile time). However do note
+ that the offset in the bitstring is usually not known.
+
+(17) PARTLY DONE - Fix the META file. Current one is very broken.
+
+(18) DONE - check() qualifier:
+
+ { field : 16 : check (field > 100) }
+
+ The check(expr) qualifier will abort the rest of the match if the
+ expression is false.
+
+(19) DONE - bind() qualifier:
+
+ { field : 16 : bind (field * 3) }
+ ^pattern ^new value
+
+ The bind(expr) qualifier binds the pattern to a new value,
+ equivalent to doing:
+
+ let field = field * 3 in
+ (* remainder of match *)
+
+ There is a question of whether bind() should run before or
+ after when() [best is probably when() first, then bind()].
+
+(20) DONE - save_offset_to() qualifier:
+
+ { field : 16 : save_offset_to (offset), bind (field - offset) }
+
+ or:
+
+ { field : 16 : save_offset_to (field_offset) } ->
+ printf "the offset of field (%d) is %d\n" field field_offset
+
+ save_offset_to(patt) binds the current match offset to
+ the variable, for later use within bind(), when() or
+ any later parts of the match.