On Fri, Oct 30, 2015 at 1:34 PM, Tomas Lycken <tomas.lyc...@gmail.com> wrote:
>> `const A = T` is what `typealias A T` lowered to when it doesn't have type
>> parameters
>
> I wanted to inspect the output of this lowering pass, but `@code_lowered`
> was apparently not what I was looking for (at least, `@code_lowered
> :(typealias Foo Int)` didn't work...).
>
> However, I understand your statement as follows:
>
> `typealias A T` is equivalent to `const A = T`, while `typealias A{S} T{S}`
> does something more involved? What does `typealias A{S} T{Foo,S}` do? I
> assume these are not possible using `const <foo> = <bar>` constructs, right?right. Try `expand(:(typealias A B))` > > // T > > On Friday, October 30, 2015 at 1:45:37 PM UTC+1, Yichao Yu wrote: >> >> On Fri, Oct 30, 2015 at 8:29 AM, FANG Colin <coli...@gmail.com> wrote: >> > I have got the same confusion. Any ideas? >> > >> > I have even seen usage of A = T (no const) >> > (http://docs.julialang.org/en/release-0.4/manual/types/#type-unions), is >> > it >> > supposed to be bad (slow) because it is a global variable? >> > >> >> no const will have performance issue since it's a global. >> `const A = T` is what `typealias A T` lowered to when it doesn't have >> type parameters. In this case, it's just a matter of style. Being >> consistent within a file is probably better but you can pick whichever >> you prefer. >> >> > >> > >> > On Thursday, November 6, 2014 at 3:38:41 PM UTC, Steven G. Johnson >> > wrote: >> >> >> >> Given a type T, what is the difference in practice between >> >> typealias A T >> >> and >> >> const A = T >> >> ? >> >> >> >> There seems to be some disagreement over which one to use (e.g. >> >> >> >> https://github.com/JuliaLang/Compat.jl/commit/8211e38ac7d8448298a2bb3ab36d6f0b6398b577). >> >> >> >> My impression is that there is no difference, and that the only >> >> advantage >> >> of a typealias is that it can be parameterized. Is that right? >> >> >> >> If they are equivalent, what is the Julian style? Even in Julia Base >> >> it >> >> doesn't seem to be entirely consistent.
