Array Masked Array Assignment

Using an array constructor and the WHERE statement, implement the following algorithm for finding prime numbers:

1. define a vector, Prime, of size n,
2. initialise Prime such that Prime(i) = i for i = 1,n
3. set i = 2
4. for all , ( ) if Prime(j) is exactly divisible by i then set Prime(j) = 0, [hint: use the MOD (remainder) intrinsic in conjunction with a WHERE statement.]
5. increment i,
6. if i equals n then exit
7. if Prime(i) is zero then goto step 5
8. goto step 4

Print out all non-zero entries of the vector (the prime numbers).

Hint: the WHERE statement is an array assignment statement and not a control construct therefore it cannot contain a PRINT statement. The PACK intrinsic can accept an array argument and a conformable MASK and will return a 1D vector of all the elements of the array where the corresponding mask elements are .TRUE..

  Print*, PACK(Array,Mask)

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