New answers tagged primes
2
APL, 9 chars/bytes
2≡≢∪∨∘⍳⍨⎕
get the input
⎕
compute least common divisor between n and all integers from 1 to n
∨∘⍳⍨
count of unique values
≢∪
if it's exactly 2, then it's prime
2≡
0
Symbolic Raku, 17 bytes
$_=?($_%%[^] ^$_)
Try it online!
Suprisingly, this is shorter than the my previous Raku answer, though one byte longer than using the built-in
Explanation:
$_= # Set the output to
?( ) # The boolean of
$_ # If the input is
%% # Divisible by
[^] # Only one ...
0
tq, 10 bytes
?-1!xp*p%?
Explanation
Uses Wilson's theorem to do the prime-checking.
?-1! # Generate all numbers from 2 to input - 1
x, # Preserve this value, prevent it from being printed
p*p # Generate all possible combinations of those numbers
%? # Does the product of any combination equal to the input?
0
Spice, 93 bytes
;i;m;t;c;r@REA i;ADD 0 1 c;SUB i 1 m;ADD c 1 c;MOD i c t;SWI t 1 9;SWI c m 3;ADD 0 1 r;OUT r;
This outputs [1] for a prime, and [] for a non-prime.
Un-golfed explanation:
;i;m;t;c;r@ - Declare vars (@ marks end of declarations)
(line 0) REA i; - Read input into i
(line 1) ADD 0 1 c; - Set counter c = 1
(line 2) SUB i 1 m; - Set ...
1
W d, 5 bytes
(Possibly the only <=5-byter that does not use a prime or number factorization built-in?)
⊂ℝ]Aא
Unpacked:
m!Wk2=
And, just for the lols (explanation for this program is also below, without the implicitly provided ba):
W d, 13 7 bytes
W doesn't have a boring primalty test operation, which is why this program is so long. (IMO a 7-byte ...
0
Wren, 48 43 bytes
I feel surprised that I think better when using W instead of Wren. Also, the 1-primalty problem is fixed.
Fn.new{|i|(1..i).where{|x|i%x==0}.count==2}
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