# Is it a bug in comprehension?
**URL:** https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725
**Category:** General Usage
**Created:** [May 5, 2018, 11:48am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725 "2018-05-05T11:48:04Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 5, 2018, 11:48am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/1 "2018-05-05T11:48:04Z")
I got… hmmm… let’s call interesting behavior with the comprehension but only in function:
```julia
function foo(tmax, a, b, M, N)
println("1: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
tpts = [tmax/M*i for i in 0:N]
println("2: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
xpts = [a+(b-a)/N*j for j in 0:M]
println("3: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
return (tpts, xpts)
end
```
And then:
```julia
(t1, x1) = foo(1.0, -1.0, 2.0, 10, 10);
```
produces
```julia
1: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
2: a=-1.0, b=0.0, tmax = 1.0, M = 10, N = 10
3: a=-1.0, b=0.0, tmax = 1.0, M = 10, N = 10
```
Coefficient `b` got turned to zero after the first comprehension. (Julia 0.6.2 on Windows) Can anyone else confirm it?
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [May 5, 2018, 11:53am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/2 "2018-05-05T11:53:33Z")
That is odd, and I can’t reproduce it on Linux (0.6.2 nor 0.7-dev). What do get as return for `x1`?
I get
```julia
julia> x1'
1×11 LinearAlgebra.Adjoint{Float64,Array{Float64,1}}:
-1.0 -0.7 -0.4 -0.1 0.2 0.5 0.8 1.1 1.4 1.7 2.0
```
Maybe someone else with a windows install can check too.
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [May 5, 2018, 11:56am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/3 "2018-05-05T11:56:48Z")
```julia
_
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_) | Documentation: https://docs.julialang.org
_ _ _| |_ __ _ | Type "?help" for help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.6.2 (2017-12-13 18:08 UTC)
_/ |\ __'_|_|_|\__'_| | Official http://julialang.org/ release
|__/ | x86_64-w64-mingw32
julia> function foo(tmax, a, b, M, N)
println("1: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
tpts = [tmax/M*i for i in 0:N]
println("2: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
xpts = [a+(b-a)/N*j for j in 0:M]
println("3: a=$a, b=$b, tmax = $tmax, M = $M, N = $N")
return (tpts, xpts)
end
foo (generic function with 1 method)
julia> (t1, x1) = foo(1.0, -1.0, 2.0, 10, 10);
1: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
2: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
3: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
```
---
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 5, 2018, 1:20pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/4 "2018-05-05T13:20:08Z")
Interesting… I have exact same version of Julia.
However, I remember that about a month or two ago I was playing with PackageComiler.jl and I may have replaced original Julia image. Is there a way to check this?
---
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 5, 2018, 1:22pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/5 "2018-05-05T13:22:11Z")
> [@mauro3](#):
>
> What do get as return for x1?
I get the range from -1.0 to 0.0. In fact, this is how I got onto this: I was generating the range like this only to see incorrect boundaries.
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [May 5, 2018, 1:54pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/6 "2018-05-05T13:54:39Z")
Well if you have recompiled other stuff into julia then all bets are off. I suggest you download a new fresh version.
---
### Author:  [@Seif\_Shebl](https://discourse.julialang.org/u/Seif_Shebl)
#### Post date: [May 5, 2018, 4:31pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/7 "2018-05-05T16:31:26Z")
```julia
Julia Version 0.6.0
Commit 903644385b* (2017-06-19 13:05 UTC)
Platform Info:
OS: Windows (x86_64-w64-mingw32)
CPU: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, haswell)
1: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
2: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
3: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
```
Also,
```julia
Julia Version 0.7.0-DEV.5012
Commit 4339f7416a* (2018-05-05 21:39 UTC)
Platform Info:
OS: Windows (x86_64-w64-mingw32)
CPU: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, haswell)
(t1, x1) = foo(1.0, -1.0, 2.0, 10, 10);
1: a=-1.0, b=2.0, tmax = 1.0, M = 10, N = 10
2: a=-1.0, b=0.0, tmax = 1.0, M = 10, N = 10
3: a=-1.0, b=0.0, tmax = 1.0, M = 10, N = 10
```
---
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 6, 2018, 11:28am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/8 "2018-05-06T11:28:27Z")
Interesting that in 0.7 comprehension also destroys `b`.
---
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 6, 2018, 11:41am UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/9 "2018-05-06T11:41:35Z")
I can confirm the problem on
```julia
Julia Version 0.7.0-DEV.4690
Commit 78c7d87369* (2018-03-23 22:25 UTC)
Platform Info:
OS: Windows (x86_64-w64-mingw32)
CPU: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, broadwell)
Environment:
```
but not on JuliaBox with
```julia
Julia Version 0.6.2
Commit d386e40c17 (2017-12-13 18:08 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Xeon(R) CPU E5-2673 v3 @ 2.40GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.9.1 (ORCJIT, haswell)
```
> [@kristoffer.carlsson](#):
>
> Well if you have recompiled other stuff into julia then all bets are off. I suggest you download a new fresh version.
Re-installing clean Julia solved it on 0.6.2. It did look like I have replaced Julia’s image while playing with PackageCompiler.
**EDIT:** [Submitted an issue](https://github.com/JuliaLang/julia/issues/27004)
---
### Author:  [@tomaklutfu](https://discourse.julialang.org/u/tomaklutfu)
#### Post date: [May 6, 2018, 5:50pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/10 "2018-05-06T17:50:07Z")
Would it be Windows specific? All failures are in mingw environment.
---
### Author:  [@mobius-eng](https://discourse.julialang.org/u/mobius-eng)
#### Post date: [May 6, 2018, 9:23pm UTC](https://discourse.julialang.org/t/is-it-a-bug-in-comprehension/10725/11 "2018-05-06T21:23:06Z")
> [@tomaklutfu](#):
>
> Would it be Windows specific? All failures are in mingw environment.
This seems to be the case. I don’t have other systems to test elsewhere.