Peter Goodall (Nov 16 2021 at 00:46): Peter Goodall (Nov 16 2021 at 00:46):I am trying to create a Bit type - I'm not interested in efficiency - I'm playing with a proof of bitstrings with XOR as an Abelian Group.
Why are \ttone and \ttzero invalid characters? I'm getting them from https://docs.julialang.org/en/v1/manual/unicode-input/
fails:
julia> @enum 𝔹 𝟶 𝟷
ERROR: syntax: invalid character "𝟶" near column 9
Stacktrace:
[1] top-level scope
@ none:1
julia> typeof(𝟷)
ERROR: syntax: invalid character "𝟷" near column 8
Stacktrace:
[1] top-level scope
@ none:1
works:
julia> @enum 𝔹 α β
I can't find any contradiction in Julia - Allowed Variable Names
\ttzero = U+1D7F6
Sukera (Nov 16 2021 at 08:08):seems like a parsing error
Sebastian Pfitzner (Nov 16 2021 at 08:56):number-like chars are usually not allowed to start an identifier
Sebastian Pfitzner (Nov 16 2021 at 08:56):so a𝟶 parses fine
Sukera (Nov 16 2021 at 08:59):right, \ttone is not a letter
julia> '𝟷'
'𝟷': Unicode U+1D7F7 (category Nd: Number, decimal digit)
maybe a string macro for creating your "bitstrings" is better suited?
Peter Goodall (Nov 16 2021 at 18:34):@Sebastian Pfitzner That looks like what the parser was complaining about, but the documentation says:
Allowed Variable Names
Variable names must begin with a letter (A-Z or a-z), underscore, or a subset of Unicode code points greater than 00A0
And then (IMHO) it mumbles a bit...
Sebastian Pfitzner (Nov 16 2021 at 18:34):It does say "Subsequent characters may also include ! and digits (0-9 and other characters in categories Nd/No)", which kinda implies that those are not allowed at the start
Peter Goodall (Nov 16 2021 at 18:38):My lack of unicode experience is showing... Unicode Categories are now decrypted for me.
List of Unicode Characters of Category “Decimal Number”
Peter Goodall (Nov 16 2021 at 18:42):Sort of happy with this:
> @enum 𝔹 zero one
> ⊻(a::𝔹, b::𝔹) = a == b ? zero : one
⊻ (generic function with 1 method)
> @show (zero ⊻ one, one ⊻ one)
(zero ⊻ one, one ⊻ one) = (one, zero)
you're kind of punning the functions zero and one though
Sukera (Nov 16 2021 at 18:55):julia is very unicode aware
Peter Goodall (Nov 16 2021 at 19:42):@Sukera
you're kind of punning the functions
zeroandonethough
I'm not sure what you mean by functions. I thought I was defining a data-type with two elements zero and one, which I am giving behavior by defining the function ⊻.
Cheers...
Sebastian Pfitzner (Nov 16 2021 at 19:47):that will locally shadow the one/zero functions that Base exports
Sebastian Pfitzner (Nov 16 2021 at 19:47):which isn't necessarily bad though
Peter Goodall (Nov 16 2021 at 19:48):If do:
julia> typeof(zero)
Enum 𝔹:
zero = 0
one = 1
The enumeration, to my mind - coincidentally, assigns them integers corresponding to their 'emotional' value.
This works as well:
> @enum 𝔹 zero=3 one=7
> ⊻(a::𝔹, b::𝔹) = a == b ? zero : one
> @show (zero ⊻ one, one ⊻ one)
(zero ⊻ one, one ⊻ one) = (one, zero)
I could have given them boolean values - which I might like to do?
Peter Goodall (Nov 16 2021 at 19:52):oh boy...
Mason Protter (Nov 16 2021 at 19:53):Not sure what to say other than to re-iterate what Sebastian said. one and zero are functions exported by Base
julia> zero(Float64)
0.0
julia> one(Complex{Rational{Int}})
1//1 + 0//1*im
When you do
@enum 𝔹 zero one
you're locally changing the meaning of those identifiers to be what your Enum defines
Mason Protter (Nov 16 2021 at 19:53):Which is fine
Mason Protter (Nov 16 2021 at 19:53):And you can still access Base.one and Base.zero by qualifying the names
Mason Protter (Nov 16 2021 at 19:54):julia> @enum 𝔹 zero one
julia> zero(Float64)
ERROR: MethodError: objects of type 𝔹 are not callable
Stacktrace:
[1] top-level scope
@ REPL[5]:1
julia> Base.zero(Float64)
0.0
I made a joke - which I couldn't see :-))
Peter Goodall (Nov 16 2021 at 19:56):Is there a way of creating a type in Julia, which has a set of elements, without using @enum?
Though now all you kind people have shown me what I was really doing, I think for the purposes of this exercise, I have something that works.
Mason Protter (Nov 16 2021 at 20:01):You could use an inner constructor to reject invalid data
julia> struct 𝔹²
x::Int
y::Int
𝔹²(x,y) = if (x,y) ∈ Iterators.product((0,1), (0,1))
new(x,y)
else
throw("Invalid booleans $((x,y))")
end
end
julia> 𝔹²(1, 0)
𝔹²(1, 0)
julia> 𝔹²(0, 0)
𝔹²(0, 0)
julia> 𝔹²(0, 2)
ERROR: "Invalid booleans (0, 2)"
Stacktrace:
[1] 𝔹²(x::Int64, y::Int64)
@ Main ./REPL[8]:7
[2] top-level scope
@ REPL[11]:1
I found this: Style recommendation for enum as type, which has discussion on the difference between enumerated types, and types that can be dispatched apon.
Notification Bot (Nov 17 2021 at 10:44):Alexander has marked this topic as unresolved.
Notification Bot (Nov 17 2021 at 10:45):Alexander has marked this topic as resolved.
Peter Goodall (Nov 17 2021 at 21:05):from an out-of-the-box REPL:
julia> zero(true)
false
julia> zero(false)
false
julia> one(false)
true
julia> one(true)
true
Learning by Breaking
rocco sprmnt21 (Nov 17 2021 at 21:24):Sebastian Pfitzner said:
It does say "Subsequent characters may also include ! and digits (0-9 and other characters in categories Nd/No)", which kinda implies that those are not allowed at the start
"Subsequen t characters may also include ! and digits (0-9 and other characters in categories Nd/No)", implies that characters other than a-z, _, A-Z,!, 0-9, "subset of Unicode code points greater than 00A0" and so on, are not allowed either at the beginning or as subsequent characters, in my opinion.
In any case, the definition seems to me not "clean" as it speaks as allowed characters of UN SUBSET unspecified of Unicode code points greater than 00A0
It is not clear whether all code points greater than 00A0 or only some (which?) of them are intended.
Sukera (Nov 17 2021 at 21:46):yes, Bool is a Integer in julia
Mason Protter (Nov 18 2021 at 21:23):which IMO is much more sensible than the reverse where a lot of languages treat integers as booleans
Sukera (Nov 18 2021 at 21:27):yes, but only if you error when trying to index with a boolean
Sukera (Nov 18 2021 at 21:27):else writing x > 4 instead of x >> 4 in an indexing expression by accident is horrible to debug
Last updated: Dec 28 2024 at 04:38 UTC