Implemented bitwise nand and nor; tests and docs included. #40339
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base/bool.jl
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| 1 | ||
| ``` | ||
| """ | ||
| nand(x::Bool, y::Bool) = ~(x & y) |
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Have you tried this with just defining a single method as proposed in #40272? I really don't think you need to define 16 methods here.
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I tried it with just the single method but ran into issues when testing nand(missing) and nand(x) where x is an integer (trying the single-arg versions caused an error). Instead of defining 16 methods, I've defined 4:
julia> methods(nand)
# 4 methods for generic function "nand":
[1] nand(::Missing) in Base at missing.jl:101
[2] nand(a::BigInt, b::BigInt) in Base.GMP at gmp.jl:551
[3] nand(x::Integer) in Base at operators.jl:579
[4] nand(x, y) in Base at bool.jl:105This passes all the tests I've made.
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I would skip the one-arg ones as well and just have the two-arg version. nand(x) = x seems questionable to me anyways.
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I understand how nand(x) = x seems questionable, but out of curiosity, what's your thinking on nand(missing)? In my limited knowledge, it seems like we should include it since the majority of other operators have the same property. If not, is there a concept I'm missing / misunderstanding?
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For any arbitrary set of values, we can decompose these two functions essentially just directly into their constituent parts:
nand(x...) = ~(&)(x...)
nor(x...) = ~|(x...)There was a problem hiding this comment.
My initial thought was to edge on the more conservative side here and just implement the most minimal version for now. This implementation now seems like a sensible extension to me though, so we might as well go with that.
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Got it, I appreciate your help!
base/gmp.jl
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| @@ -547,6 +547,18 @@ end | |||
| (-)(x::BigInt) = MPZ.neg(x) | |||
| (~)(x::BigInt) = MPZ.com(x) | |||
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| # nand and nor | |||
| nand(a::BigInt, b::BigInt) = MPZ.com(MPZ.and(a, b)) | |||
| nand(a::BigInt, b::BigInt, c::BigInt) = nand(nand(a, b), c) | |||
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This is not what I would expect multi-arg nand to do. In all contexts I have encountered it, it was defined as ~(a & b & c). I think it would be better to just define the two-arg version for now though.
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Got it. I can remove the multi-arg versions for now.
base/promotion.jl
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| nand(x::T, y::T) where {T<:Integer} = no_op_err("nand", T) | ||
| nor(x::T, y::T) where {T<:Integer} = no_op_err("nor", T) |
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This should not be an error. The idiomatic Julia solution is to use duck-typing, so that nand/nor just work if a type defines ~ and &/|.
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Got it. I'll remove these two lines.
base/gmp.jl
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| @@ -547,6 +547,10 @@ end | |||
| (-)(x::BigInt) = MPZ.neg(x) | |||
| (~)(x::BigInt) = MPZ.com(x) | |||
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| # nand and nor | |||
| nand(a::BigInt, b::BigInt) = MPZ.com(MPZ.and(a, b)) | |||
| nor(x::BigInt, y::BigInt) = MPZ.com(MPZ.ior(x, y)) | |||
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Why are these definitions needed? Aren't they equivalent to the generic ~(x & y) and ~(x | y) fallback definitions?
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You're right, they are equivalent. I will remove them.
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Seems like there should be some specialized methods in |
simeonschaub
removed
the
merge me
Addresses #40272
Features included:
nandandnor(for single, dual, multiple arguments) similar to the implementation of bitwisexor:⊼is an alias fornand⊽is an alias fornorxor(checked many of these by computing the 256-bit binary representation of a number and wrote a script to computenandornordigit by digit). Checked usingmake test-all.make docsto confirm that it worked./base/math.mdand/manual/mathematical-operations.mdto includenandandnormake -C doc doctest=trueto check doctests (doctests were modeled afterxor).\nandand\nor;\barwedgeand\veebarare still functional.