I see. Thanks Toivo and Ivar.
On Tue, 2014-10-21 at 13:10, Ivar Nesje <[email protected]> wrote:
> This seems like a very similar issue to the various issues about the `=` in
> keyword argument parsing to a different expression than `=` in an
> assignment. They print equal, but parse to different expressions, depending
> on the context. Not sure what Jeff want to do, but it seems likely that we
> ultimately would like to use the same expressions for the same syntactic
> elements.
>
> Ivar
>
>
>
> kl. 12:54:43 UTC+2 tirsdag 21. oktober 2014 skrev Mauro følgende:
>>
>> > What is Expr(:<:, :X, :Int) supposed to mean?
>>
>> It's part of a function definition:
>>
>> :(f{X<:Int}(x::X) = 5).args[1].args[1].args[2]
>>
>> I came across this when doing unit testing for a function which picks a
>> function definition apart:
>>
>> julia> parsef(fn) = fn.args[1].args[1].args[2]
>> parsef (generic function with 1 method)
>>
>> julia> fn = :(f{X<:Int}(x::X) = 5)
>> :((f{X<:Int})(x::X) = 5)
>>
>> julia> parsef(fn)
>> :(X<:Int)
>>
>> julia> @test parsef(fn)==:(X<:Int)
>> ERROR: test failed: (X<:Int == X <: Int)
>>
>> julia> @test parsef(fn)==Expr(:<:, :X, :Int)
>> # passes test
>>
>> >
>> > I just get an AST error when trying to evaluate that expression, so it
>> > can't be very usefull
>> >
>> > julia> eval(Expr(:<:, :Int64, :Int))
>> > ERROR: unsupported or misplaced expression <:
>> >
>> > We should probably consider erroring out when printing invalid
>> expressions.
>> >
>> > Regards
>> > Ivar
>> >
>> > kl. 11:05:34 UTC+2 tirsdag 21. oktober 2014 skrev Mauro følgende:
>> >>
>> >> This seems a bit confusing:
>> >>
>> >> ```
>> >> julia> Expr(:<:, :X, :Int)
>> >> :(X<:Int)
>> >>
>> >> julia> Expr(:<:, :X, :Int).head
>> >> :<:
>> >>
>> >> julia> :(X<:Int)
>> >> :(X <: Int)
>> >>
>> >> julia> :(X<:Int).head
>> >> :comparison
>> >> ```
>> >>
>> >> Is this intentional? This also means that copy-pasting the string
>> >> representation of `Expr(:<:, :X, :Int)` does not yield itself.
>> >>
>>
>>
