No more ImaginaryUnit: const im = Complex(false,true).
#5468
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This change requires giving multiplition by Bools special behavior. Approximately, `true * x = x` and `false * x = zero(x)`, but a bit complicated for the sake of promotion, the only non-trivial example of which is `Bool * MathConst`, which is promoted to Float64. Idea originally due to @GunnarFarneback: https://groups.google.com/forum/#!topic/julia-dev/VkGrqnrAdaY #2980 #3728
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This change is hard to resist. It simplifies the code and adds nice behavior like In the issues linked above, I said I couldn't think of a justification for this. Now I might have one: a pure imaginary type behaves identically to a complex number whose real part behaves like the |
| @@ -42,6 +42,12 @@ abs2(x::Bool) = x | |||
| ^(x::Bool, y::Bool) = x|!y | |||
| ^(x::Integer, y::Bool) = y ? x : one(x) | |||
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| function *{T<:Number}(x::Bool, y::T) | |||
| S = promote_type(Bool,T) | |||
| ifelse(x, convert(S,y), convert(S,0)) | |||
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Just curious, why the use of ifelse here?
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It doesn't require a branch --- both clauses can be evaluated, which often allows better code generation.
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I like it; I don't see any use for |
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Alright. If it's good enough for @stevengj, there's not much more I could ask for. The only way we're going to find out if this is ok is by merging it. |
No more ImaginaryUnit: `const im = Complex(false,true)`.
is a lot longer than |
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Working on improving the codegen now. |
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Codegen is much improved, but it still does an unnecessary addition of |
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We were hoping to avoid a pure imaginary type. But, in addition to the codegen issue, there is also a potential bug: |
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What is |
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Steven's function |
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Ok, the core problem is that |
This change requires giving multiplition by Bools special behavior. Approximately,
true * x = xandfalse * x = zero(x), but a bit complicated for the sake of promotion, the only non-trivial example of which isBool * MathConst, which is promoted to Float64.Idea originally due to @GunnarFarneback:
Compare against #5313.