Pair printing :(get! => 4) doesn't add space to avoid ambiguity

[mauro3]

The second example should probably work:

julia> Dict(get=>5)
Dict{Function,Int64} with 1 entry:
  get => 5

julia> Dict(get!=>5)
ERROR: syntax: missing comma or ) in argument list

[JeffBezanson]

Parsing operators is greedy, so it's going to see a !=. You need to add spaces.

[mauro3]

I see. In that case, maybe add spaces to the string rep:

julia> :(get! => 4)
:(get!=>4)

julia> :(get!=>4)
ERROR: syntax: missing separator in tuple

[ivarne]

Yes, that seems reasonable. We should at least improve the heuristics so that the space is printed when it is needed.

[toivoh]

Adding a few spaces wouldn't be so bad in general. It seems possible to break all the operators listed in expr_infix in show.jl with greedy operator parsing, not just =>:

julia> :(< : 2)
:(<:2)

julia> :(< :: T)
:(<::T)

julia> :(S{< <: T})
:(S{<<:T})

julia> :((-) -> 1)
:(-->begin  # none, line 1:
            1
        end)

But it would be nice to avoid spaces around :: and ->. Maybe we should print symbols that can cause trouble (such as get! and +) in parentheses?

Another interesting one is

julia> :(+ + +)
:(+(++))

[StefanKarpinski]

How about just printing the spaces all the time? I find it much more readable and it's way simpler.

[ivarne]

Hmm.. This probably isn't a backport worthy issue, because the Pair concept is new in 0.4.