\ 2019-09-24 ruv

\ Implementation of the special "dual semantics" words

\ as STATE-dependent immediate words.

\ The following words are implemented here:

\ S" TO IS ACTION-OF

\ and the corresponding words for them:

\ VALUE DEFER DEFER@ DEFER!

\ NB: this "TO" cannot be applied to the local variables

\ NB: 2VALUE and FVALUE can be easy implemeted too,

\ with a bit modification of TO and VALUE

\ see-also: https://git.io/JvctZ

\ An initial action for a deferred word

: error-np ( -- ) -21 throw ; \ Not Provided, "unsupported operation"

\ Implementing of: 'to', 'is', 'action-of', 's"'

: value create , does> @ ;

: defer create ['] error-np , does> @ execute ;

: defer@ >body @ ;

: defer! >body ! ;

: is ' >body tt-lit ['] ! tt-xt ; immediate

: to [ ' is compile, ] ; immediate \ synonym; don't use postpone

: action-of ' >body tt-lit ['] @ tt-xt ; immediate

: s" [char] " parse tt-slit ; immediate