Linear congruential generator

module LCG {

  # Creates a linear congruential generator and remembers the initial seed.
  class Common(r) {
     has seed = r
  }

  # LCG::Berkeley generates 31-bit integers using the same formula
  # as BSD rand().
  class Berkeley < Common {
    method rand {
      self.r = ((1103515245 * self.r + 12345) & 0x7fff_ffff);
    }
  }

  # LCG::Microsoft generates 15-bit integers using the same formula
  # as rand() from the Microsoft C Runtime.
  class Microsoft < Common {
    method rand {
      self.r = ((214013 * self.r + 2531011) & 0x7fff_ffff);
      self.r >> 16;
    }
  }
}

var lcg1 = LCG::Berkeley(1)
say 5.of { lcg1.rand }

var lcg2 = LCG::Microsoft(1)
say 5.of { lcg2.rand }

Output:

[1103527590, 377401575, 662824084, 1147902781, 2035015474]
[41, 18467, 6334, 26500, 19169]

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