Thank you for the helpful advice. In this particular case, I can indeed
just do what you suggest and call @eval at the top level in my module in a
for loop. It would be useful to know explicitly why it is considered poor
form to define types inside a function; I don't think it is clear from the
follow-up link, though I found it helpful for other reasons. I'm using the
function for my own internal purposes and not exporting it.
Elsewhere in my code, I define a function to create other *functions*—not
types—based on a few parameters. My module has several includes, and in
each included file it makes sense to create functions based on some
parameters in a Dict. So in this case, I like using the function to create
other functions, because I can just call it in each included file. Is this
considered bad style? If so, what is an alternative that is comparably
concise?
On Sunday, October 11, 2015 at 3:04:25 PM UTC-7, Isaiah wrote:
>
> You are calling `symbol` on an object, which results in a fully-qualified
> name when called inside a module:
>
> julia> module Foo
> abstract a
> f() = symbol(a)
> end
>
> julia> Foo.f()
>
> symbol("Foo.a")
>
>
> (or try adding `@show superSymb` inside your function)
>
> Creating a symbol from a type instance here isn't really necessary because
> you can splice in `$supertype` directly. (see the "Metaprogramming" section
> of the manual)
>
> Having said that: calling a function to create a type is not
> recommended/idiomatic. Instead, you could call `@eval` at the top level in
> your module (possibly in a for loop). There are a handful of examples of
> this in base, for example in "linalg/triangular.jl".
>
>
>
>
> On Sun, Oct 11, 2015 at 12:01 PM, Andrew Keller <andrew.k...@gmail.com
> <javascript:>> wrote:
>
>> I'm using Julia 0.4.0 on Mac OS X 10.10.5. I'd like to put some code into
>> a module, but I'm having some trouble with namespaces. The following fails
>> (`UndefVarError: test.a not defined`) when enclosed inside `module test`.
>> When outside the module, e.g. pasted into the REPL, the code works fine.
>> Could someone point me to relevant reading material or explain what is
>> going on? It seems I can avoid the problem by putting the string "a" in
>> the dictionary instead of the abstract type, but I want to know why I am
>> unable to do things as written. Thank you for your patience as I am new to
>> the language.
>>
>> module test
>>
>> abstract a
>>
>> dict = Dict("key" => a)
>>
>> function createType(typeName::ASCIIString,supertype::DataType)
>>
>> typeSymb = symbol(typeName)
>> superSymb = symbol(supertype)
>> @eval immutable ($typeSymb){T} <: $superSymb
>>
>> num::Float64
>>
>> end
>>
>> end
>>
>> createType("b",dict["key"])
>>
>> end
>>
>
>
