Concatenate two primes is also prime: Difference between revisions

Content added Content deleted
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</pre>
</pre>


=={{header|jq}}==
{{works with|jq}}
'''Works with gojq, the Go implementation of jq'''

'''Preliminaries'''
<lang jq>def is_prime:
. as $n
| if ($n < 2) then false
elif ($n % 2 == 0) then $n == 2
elif ($n % 3 == 0) then $n == 3
elif ($n % 5 == 0) then $n == 5
elif ($n % 7 == 0) then $n == 7
elif ($n % 11 == 0) then $n == 11
elif ($n % 13 == 0) then $n == 13
elif ($n % 17 == 0) then $n == 17
elif ($n % 19 == 0) then $n == 19
else {i:23}
| until( (.i * .i) > $n or ($n % .i == 0); .i += 2)
| .i * .i > $n
end;

# Emit an array of primes less than `.`
def primes:
if . < 2 then []
else
[2] + [range(3; .; 2) | select(is_prime)]
end;

# Pretty-printing
def nwise($n):
def n: if length <= $n then . else .[0:$n] , (.[$n:] | n) end;
n;

def lpad($len): tostring | ($len - length) as $l | (" " * $l)[:$l] + .;
</lang>
'''The task'''
<lang jq># Emit [p1,p2] where p1 < p2 < . and the concatenation is prime
def concatenative_primes:
primes
| range(0;length) as $i
| range($i+1;length) as $j
| [.[$i], .[$j]], [.[$j], .[$i]]
| select( map(tostring) | add | tonumber | is_prime);

[100 | concatenative_primes | join("||")]
| (nwise(10) | map(lpad(6)) | join(" "))</lang>
{{out}}
<pre>
2||3 2||11 2||23 2||29 2||41 2||71 2||83 5||3 3||7 7||3
3||11 11||3 3||13 3||17 17||3 19||3 23||3 29||3 3||31 31||3
3||37 37||3 43||3 3||47 3||53 3||59 59||3 61||3 3||67 67||3
3||73 73||3 3||79 3||83 3||89 3||97 5||23 5||41 5||47 5||71
13||7 7||19 19||7 31||7 7||43 7||61 61||7 67||7 7||73 79||7
7||97 97||7 11||17 11||23 23||11 11||29 41||11 11||53 11||71 83||11
13||19 19||13 13||61 61||13 13||67 13||73 17||23 29||17 17||41 17||47
17||53 17||59 17||83 83||17 17||89 19||31 31||19 37||19 67||19 19||73
19||79 79||19 19||97 97||19 23||41 23||47 47||23 53||23 59||23 23||71
23||83 23||89 89||23 41||29 47||29 29||53 29||71 71||29 83||29 89||29
31||37 61||31 31||67 73||31 43||37 37||61 37||67 67||37 37||79 79||37
37||97 41||53 41||59 89||41 61||43 43||73 43||97 97||43 53||47 47||59
47||83 47||89 59||53 83||53 71||59 67||61 61||73 61||97 67||79 97||67
</pre>
=={{header|Julia}}==
=={{header|Julia}}==
<lang julia>using Primes
<lang julia>using Primes
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foreach(p -> print(lpad(last(p), 5), first(p) % 16 == 0 ? "\n" : ""),
foreach(p -> print(lpad(last(p), 5), first(p) % 16 == 0 ? "\n" : ""),
catprimes() |> enumerate)
catprimes() |> enumerate)
</lang>{{out}}<pre>
</lang>{{out}}
<pre>
23 37 53 73 113 137 173 193 197 211 223 229 233 241 271 283
23 37 53 73 113 137 173 193 197 211 223 229 233 241 271 283
293 311 313 317 331 337 347 353 359 367 373 379 383 389 397 433
293 311 313 317 331 337 347 353 359 367 373 379 383 389 397 433
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