# Prime Numbers in F# QuickStart Sample

Illustrates working with prime numbers and the IntegerMath class in the Extreme.Mathematics namespace in F#.

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``````// Illustrates working with prime numbers using the
// IntegerMath class in the Extreme.Mathematics
// namespace of Extreme Numerics.NET.

#light

open System

// We use many classes from the Extreme.Mathematics
// namespace.
open Extreme.Mathematics

// The license is verified at runtime. We're using a demo license here.
// https://numerics.net/trial-key

//
// Factoring numbers
//

let printFactors n factors =
printf "%d = " n
for factor in factors do
match factor with
| struct (p, 1) -> printf " * %d" p
| struct (p, n) -> printf " * %d^%d" p n
printfn ""
let printLongFactors n factors =
printf "%d = " n
for factor in factors do
match factor with
| struct (p, 1) -> printf " * %d" p
| struct (p, n) -> printf " * %d^%d" p n
printfn ""

let n = 1001110110
let factors = IntegerMath.Factor(n)
printFactors n factors

// Factors that occur multiple times is repeated as many times as necessary:
let n2 = 256 * 6157413
let factors2 = IntegerMath.Factor(n2)
printFactors n2 factors2

// The 64bit version can safely factor numbers up to 48 bits long:
let n3 = 1296523L * 1177157L
let factors3 = IntegerMath.Factor(n3)
printLongFactors n3 factors3

//
// Prime numbers
//

// The IsPrime method verifies if a number is prime or not.
let p1 = 801853937
printfn "%d is prime? %b!" p1 (IntegerMath.IsPrime(p1))
let p2 = 801853939
printfn "%d is prime? %b!" p2 (IntegerMath.IsPrime(p2))

// MextPrime gets the first prime after a specified number.
// You can call it repeatedly to get successive primes.
// Let//s get the 10 smallest primes larger than one billion:
let mutable pn = 1000000000
printfn "\nFirst 10 primes greater than 1 billion:"
for index in 1..10 do
pn <- IntegerMath.NextPrime(pn)
printf "%16d" n
printfn ""

// PreviousPrime gets the last prime before a specified number.
pn <- 1000000000
printfn "Last 10 primes less than 1 billion:"
for index in 1..10 do
pn <- IntegerMath.PreviousPrime(pn)
printf "%16d" n
printfn ""

printf "Press Enter key to exit..."