\ Structural Conditionals, based on branches 12dec92py
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: ?struc ( flag -- ) abort" unstructured " ;
: sys? ( sys -- ) dup 0= ?struc ;
: >mark ( -- sys ) here 0 , ;
: >resolve ( sys -- ) here over - swap ! ;
: <resolve ( sys -- ) here - , ;
: BUT sys? swap ; immediate restrict
: YET sys? dup ; immediate restrict
\ Structural Conditionals 12dec92py
: AHEAD postpone branch >mark ; immediate restrict
: IF postpone ?branch >mark ; immediate restrict
: THEN sys? dup @ ?struc >resolve ; immediate restrict
: ELSE sys? postpone AHEAD swap postpone THEN ;
' THEN Alias ENDIF immediate restrict
: BEGIN here ; immediate restrict
: WHILE sys? postpone IF swap ; immediate restrict
: AGAIN sys? postpone branch <resolve ; immediate restrict
: UNTIL sys? postpone ?branch <resolve ; immediate restrict
: REPEAT over 0= ?struc postpone AGAIN postpone THEN ;