Legendre prime counting function: Difference between revisions
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</pre>
=={{header|Ruby}}==
{{trans|Wren}}
<syntaxhighlight lang="ruby">require 'prime'
def pi(n)
@pr = Prime.each(Integer.sqrt(n)).to_a
a = @pr.size
case n
when 0,1 then 0
when 2 then 1
else phi(n,a) + a - 1
end
end
def phi(x,a)
case a
when 0 then x
when 1 then x-(x>>1)
else
pa = @pr[a-1]
return 1 if x <= pa
phi(x, a-1)- phi(x/pa, a-1)
end
end
(0..9).each {|n| puts "10E#{n} #{pi(10**n)}" }
</syntaxhighlight>
{{out}}
<pre>10E0 0
10E1 4
10E2 25
10E3 168
10E4 1229
10E5 9592
10E6 78498
10E7 664579
10E8 5761455
10E9 50847534
</pre>
=={{header|Sidef}}==
<syntaxhighlight lang="ruby">func legendre_phi(x, a) is cached {
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