[julia-users] Append! resulting in #undef elements. Intended behavior?
Hi List!
I'm a particle physicist just getting started with some julia. I've been
using some python in the past but now I'm trying to use analyzing some lab
data as an excuse to learn Julia.
So far it looks like I'm going to stick with it for a while.
I've been trying to play with basic image analysis, and I've come across
the following behavior: append! complains that it doesn't find a suitable
method for my call signature, but it does append an #undef. Is this
intended?
Please see below for a session.
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_)| Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type help() to list help topics
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.3.0-rc1 (2014-07-14 02:04 UTC)
_/ |\__'_|_|_|\__'_| |
|__/ | x86_64-apple-darwin13.3.0
julia x = Array[]
0-element Array{Array{T,N},1}
julia append!(x, Array[1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}}, ::Int64)
in getindex at array.jl:121
julia x
0-element Array{Array{T,N},1}
julia append!(x, Array[[1]])
1-element Array{Array{T,N},1}:
[1]
julia append!(x, [1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}}, ::Int64)
in copy! at abstractarray.jl:197
in append! at array.jl:475
julia x
2-element Array{Array{T,N},1}:
[1]
#undef
Re: [julia-users] Append! resulting in #undef elements. Intended behavior?
Hi Jan,
You have your syntax a little mixed up. The usage of:
Type[]
actually declares an empty array with element type of `Type`. So you're
first line:
x = Array[]
is actually creating an array of arrays.
Likewise, you're seeing the error in
Array[1]
Because you're trying to put an Int[1] array into an array of arrays (and
julia doesn't know how to make that conversion).
The last error is unfortunate, because it seems that the call to `append!`
is allocating space for the array you're appending but then fails when
actually trying to put the 2nd array into the newly allocated space.
Because `append!` is mutating, you're left with your original array mutated
with the extra space, with the #undef.
I think the semantics you're looking for are as follows:
x = Int[] # declares an empty 1-d array with element type of `Int`
y = [1, 2, 3] # literal syntax for creating an array with elements, (1, 2,
3). Type inference figures out that the elements are of type `Int`
append!(x,y) # mutates the `x` array by appending all the elements of y to
it; this works because they're both of the same type
push!(x, 5) # adds a single element, 5, to the `x` array
Feel free to read through the section in teh manual on arrays to get a
better feel for what's going on.
http://docs.julialang.org/en/latest/manual/arrays/
Cheers,
-Jacob
On Thu, Jul 17, 2014 at 8:21 AM, Jan Strube jan.str...@gmail.com wrote:
Hi List!
I'm a particle physicist just getting started with some julia. I've been
using some python in the past but now I'm trying to use analyzing some lab
data as an excuse to learn Julia.
So far it looks like I'm going to stick with it for a while.
I've been trying to play with basic image analysis, and I've come across
the following behavior: append! complains that it doesn't find a suitable
method for my call signature, but it does append an #undef. Is this
intended?
Please see below for a session.
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_)| Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type help() to list help topics
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.3.0-rc1 (2014-07-14 02:04 UTC)
_/ |\__'_|_|_|\__'_| |
|__/ | x86_64-apple-darwin13.3.0
julia x = Array[]
0-element Array{Array{T,N},1}
julia append!(x, Array[1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in getindex at array.jl:121
julia x
0-element Array{Array{T,N},1}
julia append!(x, Array[[1]])
1-element Array{Array{T,N},1}:
[1]
julia append!(x, [1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in copy! at abstractarray.jl:197
in append! at array.jl:475
julia x
2-element Array{Array{T,N},1}:
[1]
#undef
Re: [julia-users] Append! resulting in #undef elements. Intended behavior?
The fact that append! grows the array on failure seems like a bug
nonetheless. If convert throws it seems preferable to leave the array as
is. I'll file an issue.
Simon
On Thursday, July 17, 2014 9:34:21 AM UTC-4, Jacob Quinn wrote:
Hi Jan,
You have your syntax a little mixed up. The usage of:
Type[]
actually declares an empty array with element type of `Type`. So you're
first line:
x = Array[]
is actually creating an array of arrays.
Likewise, you're seeing the error in
Array[1]
Because you're trying to put an Int[1] array into an array of arrays (and
julia doesn't know how to make that conversion).
The last error is unfortunate, because it seems that the call to `append!`
is allocating space for the array you're appending but then fails when
actually trying to put the 2nd array into the newly allocated space.
Because `append!` is mutating, you're left with your original array mutated
with the extra space, with the #undef.
I think the semantics you're looking for are as follows:
x = Int[] # declares an empty 1-d array with element type of `Int`
y = [1, 2, 3] # literal syntax for creating an array with elements, (1,
2, 3). Type inference figures out that the elements are of type `Int`
append!(x,y) # mutates the `x` array by appending all the elements of y
to it; this works because they're both of the same type
push!(x, 5) # adds a single element, 5, to the `x` array
Feel free to read through the section in teh manual on arrays to get a
better feel for what's going on.
http://docs.julialang.org/en/latest/manual/arrays/
Cheers,
-Jacob
On Thu, Jul 17, 2014 at 8:21 AM, Jan Strube jan.s...@gmail.com
javascript: wrote:
Hi List!
I'm a particle physicist just getting started with some julia. I've been
using some python in the past but now I'm trying to use analyzing some lab
data as an excuse to learn Julia.
So far it looks like I'm going to stick with it for a while.
I've been trying to play with basic image analysis, and I've come across
the following behavior: append! complains that it doesn't find a suitable
method for my call signature, but it does append an #undef. Is this
intended?
Please see below for a session.
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_)| Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type help() to list help topics
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.3.0-rc1 (2014-07-14 02:04 UTC)
_/ |\__'_|_|_|\__'_| |
|__/ | x86_64-apple-darwin13.3.0
julia x = Array[]
0-element Array{Array{T,N},1}
julia append!(x, Array[1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in getindex at array.jl:121
julia x
0-element Array{Array{T,N},1}
julia append!(x, Array[[1]])
1-element Array{Array{T,N},1}:
[1]
julia append!(x, [1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in copy! at abstractarray.jl:197
in append! at array.jl:475
julia x
2-element Array{Array{T,N},1}:
[1]
#undef
Re: [julia-users] Append! resulting in #undef elements. Intended behavior?
https://github.com/JuliaLang/julia/issues/7642
Re: [julia-users] Append! resulting in #undef elements. Intended behavior?
Thank you for reporting the issue.
I wasn't sure, but I thought I'd mention this as long as it's still a RC.
Jan
On Friday, July 18, 2014 4:55:36 AM UTC+9, Simon Kornblith wrote:
The fact that append! grows the array on failure seems like a bug
nonetheless. If convert throws it seems preferable to leave the array as
is. I'll file an issue.
Simon
On Thursday, July 17, 2014 9:34:21 AM UTC-4, Jacob Quinn wrote:
Hi Jan,
You have your syntax a little mixed up. The usage of:
Type[]
actually declares an empty array with element type of `Type`. So you're
first line:
x = Array[]
is actually creating an array of arrays.
Likewise, you're seeing the error in
Array[1]
Because you're trying to put an Int[1] array into an array of arrays (and
julia doesn't know how to make that conversion).
The last error is unfortunate, because it seems that the call to
`append!` is allocating space for the array you're appending but then fails
when actually trying to put the 2nd array into the newly allocated space.
Because `append!` is mutating, you're left with your original array mutated
with the extra space, with the #undef.
I think the semantics you're looking for are as follows:
x = Int[] # declares an empty 1-d array with element type of `Int`
y = [1, 2, 3] # literal syntax for creating an array with elements, (1,
2, 3). Type inference figures out that the elements are of type `Int`
append!(x,y) # mutates the `x` array by appending all the elements of y
to it; this works because they're both of the same type
push!(x, 5) # adds a single element, 5, to the `x` array
Feel free to read through the section in teh manual on arrays to get a
better feel for what's going on.
http://docs.julialang.org/en/latest/manual/arrays/
Cheers,
-Jacob
On Thu, Jul 17, 2014 at 8:21 AM, Jan Strube jan.s...@gmail.com wrote:
Hi List!
I'm a particle physicist just getting started with some julia. I've been
using some python in the past but now I'm trying to use analyzing some lab
data as an excuse to learn Julia.
So far it looks like I'm going to stick with it for a while.
I've been trying to play with basic image analysis, and I've come across
the following behavior: append! complains that it doesn't find a suitable
method for my call signature, but it does append an #undef. Is this
intended?
Please see below for a session.
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_)| Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type help() to list help topics
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.3.0-rc1 (2014-07-14 02:04 UTC)
_/ |\__'_|_|_|\__'_| |
|__/ | x86_64-apple-darwin13.3.0
julia x = Array[]
0-element Array{Array{T,N},1}
julia append!(x, Array[1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in getindex at array.jl:121
julia x
0-element Array{Array{T,N},1}
julia append!(x, Array[[1]])
1-element Array{Array{T,N},1}:
[1]
julia append!(x, [1])
ERROR: `convert` has no method matching convert(::Type{Array{T,N}},
::Int64)
in copy! at abstractarray.jl:197
in append! at array.jl:475
julia x
2-element Array{Array{T,N},1}:
[1]
#undef
