47 lines
1.4 KiB
Forth
47 lines
1.4 KiB
Forth
\ genexp-rcode.fs Generator/Exponential for RosettaCode.org
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\ Generator/filter implementation using return stack as continuations stack
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: ENTER ( cont.addr -- ;borrowed from M.L.Gasanenko papers)
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>R
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;
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: | ( f -- ;true->go ahead, false->return into generator )
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IF EXIT THEN R> DROP
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;
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: GEN ( -- ;generate forever what is between 'GEN' and ';' )
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BEGIN R@ ENTER AGAIN
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;
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: STOP ( f -- ;return to caller of word that contain 'GEN' )
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IF R> DROP R> DROP R> DROP THEN
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;
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\ Problem at hand
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: square ( n -- n^2 ) dup * ;
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: cube ( n -- n^3 ) dup square * ;
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\ Faster tests using info that tested numbers are monotonic growing
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VARIABLE Sqroot \ last square root
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VARIABLE Cbroot \ last cubic root
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: square? ( u -- f ;test U for square number)
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BEGIN
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Sqroot @ square over <
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WHILE
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1 Sqroot +!
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REPEAT
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Sqroot @ square =
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;
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: cube? ( u -- f ;test U for cubic number)
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BEGIN
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Cbroot @ cube over <
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WHILE
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1 Cbroot +!
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REPEAT
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Cbroot @ cube =
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;
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VARIABLE Counter
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: (go) ( u -- u' )
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GEN 1+ Counter @ 30 >= STOP
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dup square? | dup cube? 0= | Counter @ 20 >= 1 Counter +! | dup .
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;
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:noname 0 Counter ! 1 Sqroot ! 1 Cbroot ! 0 (go) drop ;
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execute cr bye
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