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Re: project euler problems in forth

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WJ wrote:

> > Find the sum of all the primes below two million.
> > 
> > 010.fs
> > 
> > #! /usr/bin/gforth
> > 
> > include isprime.fs
> > 
> > isprime.fs
> > 
> > : isprime ( n -- isprime )
> > dup 2 mod ( check for even)
> > if 
> >   dup 8 < ( check for < 8 - all odd are prime apart from 1)
> >   if 
> >     dup 1 = 1+ ( check for == 1)
> >   else
> >     3 ( start with divisor of 3) 
> >     begin
> >       2dup mod ( check for n mod k)
> >       if
> >         2dup dup * > ( check for k*k > n)
> >         if 
> >           2 + 0  ( bump k and restart loop)
> >         else 
> >           1 1 ( set isprime and terminate loop)
> >         then
> >       else
> >         0 1 ( clear isprime and terminate loop)
> >       then
> >     until
> >     swap drop 
> >   then
> > else 
> >   dup 2 = 0= 1+ ( check for == 2 )
> > then
> > swap drop ( drop all but isprime)
> > ;
> > : pe010
> > 0.
> > 2000000 0 do
> >   i isprime
> >   if
> >     i m+
> >   then
> > loop
> > d. cr
> > ;
> > 
> > pe010
> 
> Factor:
> 
> USING: locals math.primes ;
> 
> :: sum-primes-below ( n -- sum )
>   0 :> sum!
>   2
>   [ dup n < ]
>   [ dup sum + sum!
>     next-prime ]
>   while
>   drop  sum
> ;
> 
> 2,000,000 sum-primes-below .
> 
> 142913828922

Julia:

julia> mapreduce( n -> isprime(n) ? BigInt(n) : 0, +, 1:2_000_000 )
142913828922

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Re: project euler problems in forth "WJ" <w_a_x_man@yahoo.com> - 2013-07-06 05:47 +0000

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