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Write an endless generator primes() that gives 2, 3, 5, 7, 11,..…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Write an endless generator primes() that gives 2, 3, 5, 7, 11, ... A number is prime if no smaller number from 2 up to its square root divides it. Show the first ten primes.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Try each number from 2 upward. A number n is prime when no d from 2 to the whole part of the square root of n divides it. Yield the primes.
Check. The first ten primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29. The test d * d <= n is the same as d up to the square root of n, and it avoids a decimal number.
Answer: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29].
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