Factors of an integer: Difference between revisions
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It also displays a final count of the number of primes found.
This REXX version is about '''22%''' faster than the alternate REXX version (2<sup>nd</sup> version).
<lang rexx>/*REXX program displays divisors of any [negative/zero/positive] integer or a range.*/
parse arg LO HI inc . /*obtain the optional args*/
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say center('n', w) "#divisors" center('divisors', 60) /*display the header. */
say copies('═', w) "═════════" copies('═' , 60) /* " " separator. */
pn=
do k=2 until sq.k>=HI; sq.k= k*k /*memoization for squares.*/
end /*k*/
do n=LO to HI by inc; $= divs(n); #= words($) /*get list of divs; # divs*/
if $==! then do; #= !; $= ' (infinite)'; end /*handle case for infinity*/
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exit 0 /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
divs: procedure expose sq.; parse arg x 1 b;
if x<2 then do; x= abs(x); if x==1 then return 1; if x==0 then return '∞'; b=x
end
odd= x // 2 /* [↓] process EVEN or ODD ints. ___*/
do j=2+odd by 1+odd while
if x//j==0 then do; a=a j; b=x%j b; end /*÷? Add divisors to α and ß lists*/
end /*j*/ /* [↑] % ≡ integer division. ___*/
if
return a b
{{out|output|text= when using the input of: <tt> -6 200 </tt>}}
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