Meissel–Mertens constant: Difference between revisions
Created Nim solution.
(Created Nim solution.) |
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@show meissel_mertens(100_000_000) # meissel_mertens(100000000) = 0.2614972128591237
</syntaxhighlight>
=={{header|Nim}}==
{{trans|Wren}}
<syntaxhighlight lang="Nim">import std/[math, strformat, strutils]
proc initPrimes(N: static int): seq[int] =
## Initialize the list of primes.
const M = 2 * N - 1
var composite = newSeq[bool](N)
composite[0] = true # 1 is not prime.
# Conversions from index to value and value to index.
template index(n: int): int = (n - 1) shr 1
template value(idx: int): int = idx shl 1 + 1
# Fill the sieve.
var n = 3
while n * n <= M:
if not composite[n.index]:
for k in countup(n * n, M, 2 * n):
composite[k.index] = true
inc n, 2
# Build list of primes.
result = @[2]
for idx in 0..composite.high:
if not composite[idx]:
result.add idx.value
const N = 2^30
let primes = initPrimes(N)
echo "Primes added M"
echo "──────────── ──────────────"
const γ = 0.57721566490153286 # Euler–Mascheroni constant.
let primeCount = primes.len
var sum = 0.0
var count = 0
for p in primes:
let rp = 1 / p
sum += ln(1 - rp) + rp
inc count
if count mod 10_000_000 == 0 or count == primeCount:
echo &"{insertSep($count):>11} {sum+γ:.12}"
</syntaxhighlight>
{{out}}
<pre>Primes added M
──────────── ──────────────
10_000_000 0.261497212987
20_000_000 0.261497212912
30_000_000 0.261497212889
40_000_000 0.261497212878
50_000_000 0.261497212871
60_000_000 0.261497212867
70_000_000 0.261497212864
80_000_000 0.261497212862
90_000_000 0.261497212861
100_000_000 0.261497212859
105_097_565 0.261497212858
</pre>
=={{header|PARI/GP}}==
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