On Tuesday, August 18, 2015 at 2:11:40 PM UTC+2, Yichao Yu wrote:
>
> On Tue, Aug 18, 2015 at 6:49 AM, Sisyphuss <zhengw...@gmail.com
> <javascript:>> wrote:
> > I'm reading the documentation Metaprogramming chapter.
> > To me, the `$` operator is different from the one in the string
> > interpolation.
> > In the string, `$` is a runtime interpolation.
> > In the expression, `$` is a compile-time interpolation.
>
> No. Both of them happens at whenever the expression is evaluated. It
> happens for `@eval` at "compile time" because that's when the macro
> expansion happens.
>
> for i in 1:3
println("$(rand())")
end
It prints different values each iteration, so it's run-time interpolation.
> >
> > In one example provided, `ex = :(a in $:((1,2,3)) )`,
> > I find that it's equal to `ex = :(a in (1,2,3) )`.
> > So I do not see the intention of `$`.
>
> The examples are meant to show you the basic rules not necessarily the
> best/only way to do it.
>
Really don't see the rules from these examples.
>
> >
> > In the next example, there is `:a + :b` in the expression,
> > but the sum of `Symbols` is not defined. Is it wrong?
>
> It just construct an expression and to show you that the result is
> quoted symbol rather than the symbol themselves.
>
