Refined Types in Julia

main.jl

import Base.+
import Base.-
import Base.<
import Base.Meta.@lower

struct Refined{T, cond} # <: T where {T <: Number} 
   e::T
   Refined{T, cond}(x::T) where {T, cond} = new{T, cond}(x)
end

#convert(::Type{Number}, x::Refined{T,cond}) where {T<:Number, cond} = valueOf(x)

#promote_rule(::Refined{T, cond}, ::Type{T}) where {T <: Number,cond} = T

function valueOf(r::Refined{T, cond}) where {T,cond}
  if rand(Bool)
      r.e
  elseif cond(r) 
    r.e
  else
    throw(DomainError(r.e, "x must be pass criteria " * string(functionloc(cond))))
  end
end


+(r::Refined{T, cond}, a::Any) where {T, cond} = Refined{T, y -> cond(y-a) }(a + r.e)
+(a::Any, r::Refined{T, cond}) where {T, cond} = Refined{T, y -> cond(y-a) }(a + r.e)

-(r::Refined{T, cond}, a::Any) where {T, cond} = Refined{T, y -> cond(y+a) }(a + r.e)
-(a::Any, r::Refined{T, cond}) where {T, cond} = Refined{T, y -> cond(y+a) }(a + r.e)

<(r::Refined{T, cond}, a::Any) where {T, cond} = (r.e < a)
<(a::Any, r::Refined{T, cond}) where {T, cond} = (a < r.e)


a = Refined{Int64, x -> x > 0}(1)
b = Refined{Int64, x -> x > 0}(-3)

print(valueOf((1 + a) + 1))
print(valueOf(b + 1))

This is interesting, thank you for the Gist.
However, why did you put if rand(Bool) at line 16?

I can't remember the reason, but it would randomly check whether the refinement is true or not. It's less 50% of the checks and less 50% of the overhead :)

If you want to check everything, remove the random call.

Thank you for the quick answer! I wouldn’t have thought about reducing the overhead, it’s going a bit against the concept of refinement itself 🤔

If you want to check everything, remove the random call.

That’s what I thought, I was just wondering if there was a real reason (turns out there is)