Identical mutable struct `MutRange(1, 3) == MutRange(1, 3)` returns false

[baiango]

Julia Version

versioninfo()

Output

Julia Version 1.10.4
Commit 48d4fd4843 (2024-06-04 10:41 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × Intel(R) Core(TM) i5-9300H CPU @ 2.40GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, skylake)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

Installation Details

1. I downloaded the Windows 64-bit installer from https://julialang-s3.julialang.org/bin/winnt/x64/1.10/julia-1.10.4-win64.exe.
2. I used the default installation directory C:\Users\%username%\AppData\Local\Programs\Julia-1.10.4.
3. I selected the following additional tasks:
   • Create a Start Menu entry
   • Add Julia to PATH

Icons:
- 🟩 Create a Desktop shortcut
- ✅ Create a Start Menu entry
Other:
- ✅ Add Julia to PATH

4. I clicked the Finish button.

Minimum Reproducible Example

1. Create a file named asd.jl with the following content:

mutable struct Range
	start::UInt32
	finish::UInt32
end

function complement_range(input::Range, exclude::Range)::Vector{Range}
	not_overlapping::Bool = input.start > exclude.finish || input.finish < exclude.start
	if not_overlapping
		return [Range(input.start, input.finish)]
	end

	result::Vector{Range} = []
	if input.start < exclude.start
		append!(result, [Range(input.start, exclude.start)])
	end
	if input.finish > exclude.finish
		append!(result, [Range(exclude.finish, input.finish)])
	end
	return result
end

function test_complement_range()::Nothing
	result = complement_range(Range(1, 10), Range(3, 7))

	println("result::", typeof(result), ": ", result)
	println("[Range(1, 3), Range(7, 10)]::",
		typeof([Range(1, 3), Range(7, 10)]), ": ",
		"[Range(1, 3), Range(7, 10)]"
	)
	println(
		"complement_range(Range(1, 10), Range(3, 7)) == [Range(1, 3), Range(7, 10)]: ",
		complement_range(Range(1, 10), Range(3, 7)) == [Range(1, 3), Range(7, 10)]
	)

	@assert [Range(1, 3), Range(7, 10)] == result

	result = complement_range(Range(10, 20), Range(3, 7))
	@assert [Range(10, 20)] == result

	result = complement_range(Range(1, 3), Range(3, 7))
	@assert [Range(1, 3)] == result

	result = complement_range(Range(7, 10), Range(3, 7))
	@assert [Range(7, 10)] == result
end

test_complement_range()

2. Run include("asd.jl") to run the script in the Julia REPL

• or by executing cmd in the file path bar of Windows Explorer and run the file with julia asd.jl.

Expected Output

The expected output should be:

result::Vector{Range}: [Range(1, 3), Range(7, 10)]
[Range(1, 3), Range(7, 10)]::Vector{Range}: [Range(1, 3), Range(7, 10)]
complement_range(Range(1, 10), Range(3, 7)) == [Range(1, 3), Range(7, 10)]: true

Actual Output

The actual output is:

result::Vector{Range}: Range[Range(0x00000001, 0x00000003), Range(0x00000007, 0x0000000a)]
[Range(1, 3), Range(7, 10)]::Vector{Range}: [Range(1, 3), Range(7, 10)]
complement_range(Range(1, 10), Range(3, 7)) == [Range(1, 3), Range(7, 10)]: false
ERROR: LoadError: AssertionError: [Range(1, 3), Range(7, 10)] == result
Stacktrace:
 [1] test_complement_range()
   @ Main C:\PROJECT_FOLDER\asd.jl:35
 [2] top-level scope
   @ C:\PROJECT_FOLDER\asd.jl:47
in expression starting at C:\PROJECT_FOLDER\asd.jl:47

[baiango]

I tried to write complement_range(), but then got distracted by a squirrel and left it in this state.

[baiango]

Updated Minimal Reproducible Example

mutable struct MutRange
	start::Int
	finish::Int
end

struct Range # has to be mutable
	start::Int
	finish::Int
end

println(MutRange(1, 3) == MutRange(1, 3)) # false

println(Range(1, 3) == Range(1, 3)) # true

println((1, 3) == (1, 3)) # true

Julia REPL

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.10.4 (2024-06-04)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> mutable struct MutRange
           start::Int
           finish::Int
       end

julia>

julia> struct Range # has to be mutable
           start::Int
           finish::Int
       end

julia>

julia> println(MutRange(1, 3) == MutRange(1, 3)) # false
false

julia>

julia> println(Range(1, 3) == Range(1, 3)) # true
true

julia>

julia> println((1, 3) == (1, 3)) # true
true

julia>

[fredrikekre]

See https://docs.julialang.org/en/v1/base/math/#Base.:==. In particular

Falls back to ===.

[baiango]

I have encountered an issue where the comparison of mutable structs with identical field values returns false, even when using the == and === operators.

Here's a minimal reproducible example:

mutable struct MutRange
	start::UInt32
	finish::UInt32
end

println(MutRange(1, 3) == MutRange(1, 3)) # false
println(MutRange(1, 3) === MutRange(1, 3)) # false

Based on the documentation at https://docs.julialang.org/en/v1/base/math/#Base.:==, the == operator falls back to === for structs. However, in this case, both comparisons return false.

Could you please investigate this issue and provide guidance on how to correctly compare mutable structs with identical field values?

[fredrikekre]

the == operator falls back to === for structs. However, in this case, both comparisons return false.

Yes, == calls === so they return the same value.

provide guidance on how to correctly compare mutable structs

The forum at https://discourse.julialang.org/ is better suited for discussion and questions like this.