etc.prime

bool isPrime(uint n)

Returns true if n is prime, false otherwise. Note that this function uses a fast lookup table for values of n less than or equal to 0xFFFF, and trial division for numbers greater than this.

uint getPrimeLess(uint n)

Returns the greatest prime which is less than n. This function will assert if n is zero, one or two.

uint getPrimeLessEqual(uint n)

Returns the greatest prime which is less than or equal to n. This function will assert if n is zero or one.

uint getPrimeGreater(uint n)

Returns the smallest prime which is greater than n. This function will assert if the result would be too large to fit into a uint.

uint getPrimeGreaterEqual(uint n)

Returns the smallest prime which is greater than or equal to n. This function will assert if the result would be too large to fit into a uint.

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To do (future work)

• For numbers between 0x10000 and 0xFFFFFFFF, there are faster algorithms than trial division. We should probably use one.
• The remaining functions should probably throw exceptions instead of asserting.