68 lines
2.4 KiB
Factor
68 lines
2.4 KiB
Factor
! Copyright (C) 2004 Chris Double.
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!
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! Redistribution and use in source and binary forms, with or without
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! modification, are permitted provided that the following conditions are met:
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!
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! 1. Redistributions of source code must retain the above copyright notice,
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! this list of conditions and the following disclaimer.
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!
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! 2. Redistributions in binary form must reproduce the above copyright notice,
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! this list of conditions and the following disclaimer in the documentation
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! and/or other materials provided with the distribution.
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!
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! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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! INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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! FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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! DEVELOPERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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! SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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! OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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! WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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! OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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! ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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IN: lazy-examples
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USE: lazy
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USE: stack
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USE: math
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USE: lists
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USE: combinators
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USE: kernel
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USE: logic
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USE: sequences
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USE: namespaces
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: lfrom ( n -- llist )
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#! Return a lazy list of increasing numbers starting
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#! from the initial value 'n'.
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dup unit delay swap
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[ 1 + lfrom ] cons delay lcons ;
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: lfrom-by ( n quot -- llist )
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#! Return a lazy list of values starting from n, with
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#! each successive value being the result of applying quot to
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#! n.
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swap dup unit delay -rot
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[ , dup , \ call , , \ lfrom-by , ] make-list delay lcons ;
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: lnaturals 0 lfrom ;
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: lpositves 1 lfrom ;
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: levens 0 [ 2 + ] lfrom-by ;
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: lodds 1 lfrom [ 2 mod 1 = ] lsubset ;
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: lpowers-of-2 1 [ 2 * ] lfrom-by ;
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: lones 1 [ ] lfrom-by ;
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: lsquares lnaturals [ dup * ] lmap ;
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: first-five-squares 5 lsquares ltake ;
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: divisible-by? ( a b -- bool )
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#! Return true if a is divisible by b
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mod 0 = ;
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: sieve ( llist - llist )
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#! Given a lazy list of numbers, use the sieve of eratosthenes
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#! algorithm to return a lazy list of primes.
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luncons over [ divisible-by? not ]
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cons lsubset [ sieve ] cons delay >r unit delay r> lcons ;
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: lprimes 2 lfrom sieve ;
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: first-ten-primes 10 lprimes ltake llist>list ; |