Primality by Wilson's theorem: Difference between revisions
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=={{header|ALGOL W}}==
As with the APL, Tiny BASIC (and possibly others) samples, this computes the factorials mod p at each multiplication to avoid needing numbers larger than the 32 bit limit.
<lang algolw>begin
% find primes using Wilson's theorem: %
% p is prime if ( ( p - 1 )! + 1 ) mod p = 0 %
% returns true if n is a prime by Wilson's theorem, false otherwise %
% computes the factorial mod p at each stage, so as to %
% allow numbers whose factorial won't fit in 32 bits %
logical procedure isWilsonPrime ( integer value n ) ;
if n < 2 then false
else begin
integer factorialModN;
factorialModN := 1;
for i := 2 until n - 1 do factorialModN := ( factorialModN * i ) rem n;
factorialModN = n - 1
end isWilsonPrime ;
for i := 1 until 100 do if isWilsonPrime( i ) then writeon( i_w := 1, s_w := 0, " ", i );
end.</lang>
{{out}}
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<pre> ⎕CT←0 ⋄ naiveWilson {(⍺⍺¨⍵)/⍵} ⍳20
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=={{header|C}}==
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