60 lines
1.6 KiB
Nim
60 lines
1.6 KiB
Nim
import tables
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type PrimeType = int
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proc primesHashTable(): iterator(): PrimeType {.closure.} =
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iterator output(): PrimeType {.closure.} =
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# some initial values to avoid race and reduce initializations...
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yield 2.PrimeType; yield 3.PrimeType; yield 5.PrimeType; yield 7.PrimeType
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var h = initTable[PrimeType,PrimeType]()
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var n = 9.PrimeType
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let bps = primesHashTable()
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var bp = bps() # advance past 2
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bp = bps(); var q = bp * bp # to initialize with 3
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while true:
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if n >= q:
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let inc = bp + bp
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h[n + inc] = inc
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bp = bps(); q = bp * bp
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elif h.hasKey(n):
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var inc: PrimeType
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discard h.take(n, inc)
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var nxt = n + inc
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while h.hasKey(nxt): nxt += inc # ensure no duplicates
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h[nxt] = inc
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else: yield n
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n += 2.PrimeType
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output
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var num = 0
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stdout.write "The first 20 primes are: "
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var iter = primesHashTable()
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for p in iter():
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if num >= 20: break else: stdout.write(p, " "); num += 1
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echo ""
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stdout.write "The primes between 100 and 150 are: "
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iter = primesHashTable()
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for p in iter():
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if p >= 150: break
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if p >= 100: stdout.write(p, " ")
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echo ""
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num = 0
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iter = primesHashTable()
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for p in iter():
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if p > 8000: break
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if p >= 7700: num += 1
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echo "The number of primes between 7700 and 8000 is: ", num
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num = 1
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iter = primesHashTable()
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for p in iter():
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if num >= 10000:
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echo "The 10,000th prime is: ", p
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break
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num += 1
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var sum = 0
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iter = primesHashTable()
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for p in iter():
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if p >= 2_000_000:
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echo "The sum of the primes to two million is: ", sum
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break
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sum += p
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