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Factors of an integer: Difference between revisions

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Factors of an integer (view source)

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===optimized version===
This REXX version has no effective limits on the number of decimal digits in the number to be factored   [by adjusting the number of digits (precision)].
<br>This REXX version also supports negative integers and zero. ▼
 
▲<br>This REXX version also supports negative integers and zero.
It also indicates &nbsp; '''primes''' &nbsp; in the output listing as well as the number of factors.▼
 
<br>It also displays a final count of the number of primes found.▼
▲It also indicates &nbsp; '''primes''' &nbsp; in the output listing as well as the <u>number</u> of factors.
 
▲<br>It also displays a final count of the number of primes found.
<lang rexx>/*REXX program displays divisors of any [negative/zero/positive] integer or a range.*/
parse arg LO HI inc . /*obtain the optional args*/
HI= word(HI LO 20, 1); LO= word(LO 1,1); inc= word(inc 1,1) /*define the range options*/
w= length(HI) + 2; numeric digits max(9, w-2); $!= '∞' /*decimal digits for // */
@.=left('',7); @.1= "{unity}"; @.2= '[prime]'; @.$!= " {"$'∞} '" /*define some literals. */
say center('n', w) "#divisors" center('divisors', 60) /*display the header. */
say copies('═', w) "═════════" copies('═' , 60) /* " " separator. */
p#pn=0 /*count of prime numbers. */
do n=LO to HI by inc; divs $=divisors divs(n); #= words(divs$) /*get list of divs; # divs*/
if divs$==$! then do; #= $!; divs $= ' (infinite)'; end /*handle case for infinity*/
p= @.#; if n<0 then if n\==-1 then p= @.. /* " " " negative*/
if p==@.2 then p#pn= p#pn + 1 /*Prime? Then bump counter*/
say center(n, w) center('['#"]", 9) "──► " p ' ' divs$
end /*n*/ /* [↑] process a range of integers. */
say
say right(p#pn, 20) ' primes were found.' /*display the number of primes found. */
exit 0 /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
divisorsdivs: procedure; parse arg x 1 b; a= 1 /*set X and B to the 1st argument. */
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. ___*/end
odd= x // 2 /* [↓] process EVEN or ODD ints. ___*/
do j=2+odd by 1+odd while j*j<x /*divide by all the integers up to √ x */
if x//j==0 then do; a=a j; b=x%j b; end /*÷? Add factors to α and ß lists.*/
end /*j*/ /* [↑] % ≡ integer division. ___*/
if j*j==x then return a j b /*Was X a square? Then insert √ x */
return a b return a b /*return the divisors of both lists. */</lang>
{{out|output|text=&nbsp; when using the input of: &nbsp; &nbsp; <tt> -6 &nbsp; 200 </tt>}}
 
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