# project euler 27

# bool ? n
IsPrime ← memo(=1⧻°/×)
⍤⤙≍ 1 /↧≡IsPrime +41+⊸°√ ⇡40 # euler's formula

# create intervals:
-1000⇡2001 # [-1000, 1000]
-999⇡1999  # [ -999,  999]
≡₁(⊂⍢+₁(
    ⍣IsPrime0 ++⊃(°√|×⊙⊢|⋅⊣)
  )0
) ⊞⊟
/× &p&pf"number of primes: "°⊂ ⊣⍆♭₂