Ormiston pairs: Difference between revisions
Created Nim solution.
(→{{header|jq}}: def primeSieve:) |
(Created Nim solution.) |
||
Line 893:
3722 Ormiston pairs before 10000000
</pre>
=={{header|Nim}}==
<syntaxhighlight lang=Nim>import std/[algorithm, bitops, math, strformat, strutils]
type Sieve = object
data: seq[byte]
func `[]`(sieve: Sieve; idx: Positive): bool =
## Return value of element at index "idx".
let idx = idx shr 1
let iByte = idx shr 3
let iBit = idx and 7
result = sieve.data[iByte].testBit(iBit)
func `[]=`(sieve: var Sieve; idx: Positive; val: bool) =
## Set value of element at index "idx".
let idx = idx shr 1
let iByte = idx shr 3
let iBit = idx and 7
if val: sieve.data[iByte].setBit(iBit)
else: sieve.data[iByte].clearBit(iBit)
func newSieve(lim: Positive): Sieve =
## Create a sieve with given maximal index.
result.data = newSeq[byte]((lim + 16) shr 4)
func initPrimes(lim: Positive): seq[Natural] =
## Initialize the list of primes from 2 to "lim".
var composite = newSieve(lim)
composite[1] = true
for n in countup(3, sqrt(lim.toFloat).int, 2):
if not composite[n]:
for k in countup(n * n, lim, 2 * n):
composite[k] = true
result.add 2
for n in countup(3, lim, 2):
if not composite[n]:
result.add n
let primes = initPrimes(100_000_000)
func digits(n: Positive): seq[int] =
## Return the sorted list of digits of "n".
var n = n.Natural
while n != 0:
result.add n mod 10
n = n div 10
result.sort()
echo "First 30 Ormiston pairs:"
var count = 0
var limit = 100_000
for i in 1..(primes.len - 2):
let p1 = primes[i]
let p2 = primes[i + 1]
if p1.digits == p2.digits:
inc count
if count <= 30:
stdout.write &"({p1:5}, {p2:5})"
stdout.write if count mod 3 == 0: '\n' else: ' '
if count == 30: echo()
elif p1 >= limit:
echo &"Number of Ormiston pairs below {insertSep($limit)}: {count - 1}"
limit *= 10
if limit == 100_000_000:
break
</syntaxhighlight>
=={{header|Pascal}}==
| |||