Saline: Saturating Arithmetic in Crystal

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@RespiteSage using begin/rescue to recover from exception will probably be slow. In Arithmethic overflow should not raise an exception I shared the following snippet that uses llvm intrinsics for the task

lib LibIntrinsics
  fun sat_uadd8 = "llvm.uadd.sat.i8"(a : UInt8, b : UInt8) : UInt8
end

module Intrinsics
  def self.sadd(a : UInt8, b : UInt8) : UInt8
    LibIntrinsics.sat_uadd8(a, b)
  end
end

pp! a = 100_u8                     # => 100
pp! a = Intrinsics.sadd(a, 100_u8) # => 200
pp! a = Intrinsics.sadd(a, 100_u8) # => 255

Another idea that I would like to throw is that I think it should be possible to use macros to rewrite calls to + to some custom function like Intrinsics.sadd.

So Saline.eval(1 + 2 + 3) would compile to Intrinsics.sadd(Intrinsics.sadd(1, 2), 3) or something similar.

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