sieve.ijs

prime_sieve =: 3 : 0
 sieve_size =. y
 sieve =. sieve_size # 0
 indices =. i. sieve_size
 sieve =. 1 (0 1) } sieve
 result =. ''
 while. sieve_size ~: +/ sieve do. NB. while it has at least one 0
  num =. {. (-. sieve) # indices   NB. get first number not marked with 1
  result =. result, num
  divisible =. 0 = num | indices
  divisible =. divisible # indices
  sieve =. 1 divisible } sieve
 end.
 result
)

NB. adapted from Wikipedia's article on APL; O(n^2) complexity.

slower_prime =. 3 : 0
 a =. 1 + 1 }. i. y
 b =. a */ a
 c =. -. a e. ;b
 c # a
)

NB. tried to shorten it to tacit definition, but I have no idea how to merge these two lines together

shorter_slower_prime =. 3 : 0
 a =. 1 + 1 }. i. y
 (-. a e. ; a */ a) # a
)

prime_sieve 100
slower_prime 100
shorter_slower_prime 100