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\ 
\ 	RubyFORTH -- Copyright (C) 2007-8, Marc Simpson (GPL). 
\ 
\       Implement backtick, similar to ANS Forth's 'postpone'.
\ 
\ ==============================================================================

needs tools/whereis.fs

compiler
: ` peek-word in-compiler? if [compile] [compile] else [compile] compile then ;

( Backtick behaves like [compile] for words in COMPILER and like compile for   )
( words in FORTH. Its semantics are confusing at first sight, and its usage is )
( not recommended. It is supplied for users of the ANS Forth 'postpone' word.  )
(                                                                              )
( Usage is as follows. Imagine that we want to create two new words, 'ddup'    )
( and 'start'. 'ddup' will compile '2dup', 'start' will compile 'begin'.       )
( In the absence of backtick, these are implemented like so:                   )
(                                                                              )
( compiler                                                                     )
( : ddup    compile 2dup  ;                                                    )
( : start [compile] begin ;                                                    )
(                                                                              )
( With backtick, we can write the following:                                   )
(                                                                              )
( compiler                                                                     )
( : ddup  ` 2dup  ;                                                            )
( : start ` begin ;                                                            )
(                                                                              )
( Whichever scheme we choose, we can now say:                                  )
(                                                                              )
( forth                                                                        )
( : foo ddup  ... ;                                                            )
( : bar start ... ;                                                            )