\ @(#) condcomp.fth 98/01/26 1.2\ Conditional Compilation support\\ Words: STRINGS= [IF] [ELSE] [THEN] EXISTS?\\ Lifted from X3J14 dpANS-6 document. anew task-condcomp.fth : [ELSE]  ( -- )    1    BEGIN                                 \ level      BEGIN        BL WORD                           \ level $word        COUNT  DUP                        \ level adr len len      WHILE                               \ level adr len        2DUP  S" [IF]"  COMPARE 0=        IF                                \ level adr len          2DROP 1+                        \ level'        ELSE                              \ level adr len          2DUP  S" [ELSE]"          COMPARE 0=                      \ level adr len flag          IF                              \ level adr len             2DROP 1- DUP IF 1+ THEN      \ level'          ELSE                            \ level adr len            S" [THEN]"  COMPARE 0=            IF              1-                          \ level'            THEN          THEN        THEN        ?DUP 0=  IF EXIT THEN             \ level'      REPEAT  2DROP                       \ level    REFILL 0= UNTIL                       \ level    DROP;  IMMEDIATE : [IF]  ( flag -- )    0=    IF POSTPONE [ELSE]    THEN;  IMMEDIATE : [THEN]  ( -- );  IMMEDIATE : EXISTS? ( <name> -- flag , true if defined )    bl word find    swap drop; immediate