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fix #22168, im*I+I should be shown as (1+1im)*I #22169

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Merged
KristofferC merged 4 commits into from
Jun 6, 2017
Merged

fix #22168, im*I+I should be shown as (1+1im)*I #22169

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71c9725
fix #22168, `im*I+I` should be shown as `(1+1im)*I`
sunoru Jun 1, 2017
bd12d98
add test for `show(UniformScaling)`
sunoru Jun 1, 2017
026cede
check the number of terms in `show(::UniformScaling)`
sunoru Jun 1, 2017
273b121
fix the misuse of `|`
sunoru Jun 1, 2017
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1 change: 1 addition & 0 deletions base/linalg/uniformscaling.jl
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Expand Up @@ -31,6 +31,7 @@ eltype(::Type{UniformScaling{T}}) where {T} = T
ndims(J::UniformScaling) = 2
getindex(J::UniformScaling, i::Integer,j::Integer) = ifelse(i==j,J.λ,zero(J.λ))

show(io::IO, J::UniformScaling{T}) where {T<:Complex} = print(io, "$(typeof(J))\n($(J.λ))*I")
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@andreasnoack andreasnoack Jun 1, 2017

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Could we do a check for the number of terms instead? Minor use case but this would still be wrong for quaternions.

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@sunoru sunoru Jun 1, 2017

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That's true. But if we do such a check we have to deal with strings. Don't know if it's OK to do so.

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@andreasnoack andreasnoack Jun 1, 2017

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Aren't we already dealing with strings? My idea was to add the parentheses if something like ismatch(r"[0-9]+ ?\+|\- ?[0-9]+", "$(J.λ)")

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@sunoru sunoru Jun 1, 2017

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Oh I see. How about just checking r"\w+\s*\+|\-\s*\w+" as there must be + or - between terms if there are more than one term.

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@andreasnoack andreasnoack Jun 1, 2017

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That was also my first version but I think negative reals become false positives here

julia> ismatch(r"\w+\s*\+|\-\s*\w+", "-1")
true

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@sunoru sunoru Jun 1, 2017

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Ah I'm sorry. It's because of the misuse of | and we should use r"\w+\s*[\+\-]\s*\w+".

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@KristofferC KristofferC Jun 1, 2017

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Could you perhaps add tests for the things that wasn't completely right with the first regexp.

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@sunoru sunoru Jun 2, 2017

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I don't know what common things can be wrong with the first regexp, but I believe there could be situations when users define a type that doesn't contain digit-[plus/minus]-digit pattern, such as something like 1i+2j. (The current displays of complex and quaternion numbers have something like 0+0im so the first regexp always works with them.)

show(io::IO, J::UniformScaling) = print(io, "$(typeof(J))\n$(J.λ)*I")
copy(J::UniformScaling) = UniformScaling(J.λ)

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