Converting an array of Any to Float : float() -> no method one(Type{Any})

[bensadeghi]

julia> float(Any[3.0])
ERROR: no method one(Type{Any})
 in float at abstractarray.jl:315

[ivarne]

Not really sure what we should do here (should float sometimes not return a float, but an array?), but until that becomes decided, you can use convert(Array{Float64,1}, var).

[bensadeghi]

This used to work just fine, returning an array of floats.
Using a ~3 month old version of Julia:

julia> float(Any[3.0])
1-element Array{Float64,1}:
 3.0

[timholy]

It works for me on a version built yesterday.

[tkelman]

@timholy the merging of #6183 changed the behavior here.

[timholy]

Gotcha, thanks.

[JeffBezanson]

I'm not sure what this should do; the old behavior was effectively picking Float64 as a default, which doesn't make much sense:

julia> float({big(pi)})
1-element Array{Float64,1}:
 3.14159

Since float depends on what you pass it, the best we can do is return another Any array with float applied to each element, but that's not too useful. Perhaps the fuzzy-typed functions like float and complex should require numeric arrays.

[XilinJia]

I am pretty new to Julia, but it seems to me that type Any is causing confusion to everyone in this case.

It is very convenient to have a type Any as one can do things like:
julia> aa = ["a", 3.1, 4.2]
3-element Array{Any,1}:
"a"
3.1
4.2

Since one can also do
julia> bb = aa[2:end]
2-element Array{Any,1}:
3.1
4.2

the intention of bb is very clear - one wants to perform some kind of computation with these float (or real) numbers.

So in this case, bb should be allowed to be passed to
function func(xx::Array{Float64,1})
either directly without explicit convert, or with convert
float(bb)

If this can not be done, then what is the sense of having type Any?

[JeffBezanson]

It's fine with me if float(bb) works; we just need a proposal for what it actually means. For example, we could iterate over all the elements to determine the minimal floating-point type that can hold them all, but that's not very efficient.

[jiahao]

we could iterate over all the elements to determine the minimal floating-point type that can hold them all

It's not even clear what this means. If it's minimal type that can support the necessary precision, what happens to ["3.1"]? If it's minimal type given the dynamic range of values, then you'd end up with lots of Array{Float16}s, which are currently next to useless.

[JeffBezanson]

That reminds me --- float("3.1") simply picks Float64 by default, so maybe we should just go with that.

[jiahao]

I'd be fine with a Float64 default.

[andreasnoack]

@bensadeghi The problem is that it is not obvious what default element type an array like {"Jensen", [1 2; 3 4], 3.1} should have.

@JeffBezanson For an Any array x the type would then be determined by something like eltype(promote(0.0,x...)), right?

It could be pointed out that you are able to convert the vector in the example with float64.

[JeffBezanson]

Yes, you would have to reduce promote or promote_type over the values, ideally with a loop instead of ... to avoid stack overflow. This would be quite costly, but is arguably worth it if you end up with an Array{Float64} that would cause subsequent operations to be faster.

[JeffBezanson]

I came up with a meaning: convert everything to FloatingPoint, then promote the results together.

[ashleylid]

Apologies for posting on a closed topic but I wasn't able to get float(point) where point is type {Any,2} to work with ERROR: LoadError: float not defined on abstractly-typed arrays; please convert to a more specific type. So I reverted to using:
point = Array{Float32}(point)

[navid11m]

Hi
How can I convert a sym array to Float?

[KristofferC]

Please ask questions at https://discourse.julialang.org/ (also include a bit more information in your question, what package you are using etc).

[navid11m]

I had a question for you. I wrote an exercise and I wrote it symbolic and now I want to convert it to a float or integer.

…

On Tue, 6 Apr 2021, 16:10 Kristoffer Carlsson, ***@***.***> wrote: Please ask questions at https://discourse.julialang.org/ (also include a bit more information in your question, what package you are using etc). — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#6422 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ATQQQGIYBBCAB6ACYTOHG6LTHLXJDANCNFSM4AN7W7HQ> .

[KristofferC]

I understand that. The issue tracker is not a good place to ask these types of usage questions. That's why the forum at https://discourse.julialang.org/ exists. I would suggest posting your question there. And again, include more information. Just saying " I wrote an exercise and I wrote it symbolic and now I want to convert it to a float or integer" makes it very hard for anyone to understand what you are doing. Code is good to post because that is not so ambiguous.