in reply to Double your return!!!!

There's a paper on continuations here. It mentions Scheme, which is where I recall hearing of these sorts of things. I haven't programmed Scheme, but my rather weak understanding of continuations is that they're similar to C's setjmp/longjmp except that you can longjmp back to a location even if it's in a function that's already returned. I think Forth also has the ability to alter the calling stack in a way that does this sort of thing but I may be wrong.

Here's another interesting read that should make your head hurt a little.

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Double your return, In forth!
by xmath (Hermit) on Feb 19, 2003 at 08:24 UTC
    FORTH can do it indeed, by manipulating the return stack directly. For example: 

    : foo ( -- )  ." enter foo" cr  rdrop exit  ." exit foo" cr  ;
: bar ( -- )  ." enter bar" cr  foo    ." exit bar" cr  ;
: baz ( -- )  ." enter baz" cr  bar    ." exit baz" cr  ;

    [download]
    gives the output: 
    enter baz
enter bar
enter foo
exit baz

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    If your forth doesn't have rdrop, use r> drop or define it with: : rdrop r> r> drop >r ;

    I also strongly recall having seen words specifically for this purpose, but I can't find one in this forth (maybe they left it out in modern implementations)

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Re: Re: Double your return!!!!
by bsb (Priest) on Feb 19, 2003 at 05:39 UTC
    The ;=) operator should've given it away.
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