Semiprime: Difference between revisions
added REXX
Walterpachl (talk | contribs) (added REXX) |
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(and (= (length prime-factors) 2)
(= (foldl (λ (x y) (* (car x) y)) 1 prime-factors) n)))))</lang>
=={{header|REXX}}==
<lang rexx>
/* REXX ---------------------------------------------------------------
* 20.02.2014 Walter Pachl relying on prime decomposition
*--------------------------------------------------------------------*/
Call test 4
Call test 9
Call test 10
Call test 12
Call test 1679
Exit
test:
Parse Arg z
If isprime(z) Then Say z 'is semiprime' fl
Else Say z 'is NOT semiprime' fl
Return
isprime:
Parse Arg z
fl=factr(z)
Return words(fl)=2
/*----------------------------------FACTR subroutine-----------------*/
factr: procedure; parse arg x 1 z,list /*sets X&Z to arg1, LIST=''. */
if x==1 then return '' /*handle the special case of X=1.*/
j=2; call .factr /*factor for the only even prime.*/
j=3; call .factr /*factor for the 1st odd prime.*/
j=5; call .factr /*factor for the 2nd odd prime.*/
j=7; call .factr /*factor for the 3rd odd prime.*/
j=11; call .factr /*factor for the 4th odd prime.*/
j=13; call .factr /*factor for the 5th odd prime.*/
j=17; call .factr /*factor for the 6th odd prime.*/
/* [?] could be optimized more.*/
/* [?] J in loop starts at 17+2*/
do y=0 by 2; j=j+2+y//4 /*insure J isn't divisible by 3. */
if right(j,1)==5 then iterate /*fast check for divisible by 5. */
if j*j>z then leave /*are we higher than the v of Z ?*/
if j>Z then leave /*are we higher than value of Z ?*/
call .factr /*invoke .FACTR for some factors.*/
end /*y*/ /* [?] only tests up to the v X.*/
/* [?] LIST has a leading blank.*/
if z==1 then return list /*if residual=unity, don't append*/
return list z /*return list, append residual. */
/*-------------------------------.FACTR internal subroutine----------*/
.factr: do while z//j==0 /*keep dividing until we can't. */
list=list j /*add number to the list (J). */
z=z%j /*% (percent) is integer divide.*/
end /*while z··· */ /* // ?---remainder integer ÷.*/
return /*finished, now return to invoker*/</lang>
'''Output'''
<pre>4 is semiprime 2 2
9 is semiprime 3 3
10 is semiprime 2 5
12 is NOT semiprime 2 2 3
1679 is semiprime 23 73</pre>
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