Re: weird macro params issue

On Fri, May 2, 2008 at 7:18 PM, Attila Szegedi <[email protected]> wrote:
> The order of populating defaulted variables is undefined -- they're
>  being pulled out by an iterator out of a hash map. So if this worked
>  for you, then you just had blind luck so far, I'm afraid.
>
>  We could ensure the order going forward, or -- since with named-
>  argument invocations there's not really any specific order -- even
>  code it so that it fills out default expressions iteratively: go over
>  them once, resolving what it can; then repeat until it gets an
>  iteration where either (a) all default expressions got resolved or (b)
>  it got something other than an InvalidReferenceExcepion or (c) it
>  could not resolve any additional default expressions (and in this
>  case, rethrow the InvalidReferenceException for one arbitrarily chosen
>  unresolved default expression). That'd support any weird defaulting
>  dependency order as long as there are no circular references, and
>  circular references would also fall out with an
>  InvalidReferenceException.
>
>  Anyone object to having this logic in a subsequent FreeMarker release?

Just offhand, I wouldn't encourage anybody to do something like that.
It surprised me that it worked at all, actually. I would have to look
at the implementation. It seems to me that the default parameters
should be evaluated in the scope of the enclosing namespace and thus,
what Ioannis was doing should fail.

Now, of course, the current situation, that it works sometimes and
other times doesn't work, that's extremely undesirable. But to be
honest, it seems like such an overly intricate, excessively clever way
of doing things, that I would prefer for it just to always fail. :-)

I mean, seriously, is this coding pattern actually useful?

Of course, it would be better if it always worked than if it always
failed, but I think I would just tend towards it always failing.

JR



>
>
>  Attila.
>
>  On 2008.05.02., at 10:58, John Cherouvim wrote:
>
>
>
> > Hello
>  >
>  > I have this macro:
>  > <#macro test a b=a c=b>
>  >    ${a} - ${b} - ${c}
>  > </#macro>
>  >
>  > And this client code:
>  > <@test 1 /><br/>
>  > <@test 1 2 /><br/>
>  > <@test 1 2 3 /><br/>
>  >
>  > Which produces:
>  > 1 - 1 - 1
>  > 1 - 2 - 2
>  > 1 - 2 - 3
>  >
>  > Now if I just change the param names of the macro:
>  > <#macro test foo bar=foo baz=bar>
>  >    ${foo} - ${bar} - ${baz}
>  > </#macro>
>  >
>  > And keep the same client code, then the output produced is:
>  > InvalidReferenceException: Expression bar is undefined on line 20,
>  > column 31 in index.ftl.
>  > 1 - 2 - 2
>  > 1 - 2 - 3
>  >
>  > The first call fails when it tries to evaluate the baz=bar. Why is
>  > that?
>  >
>  > Also, is this usage valid in freemarker? To have parameters default to
>  > the value of other parameters. I find it very useful for some use
>  > cases.
>  >
>  > thanks,
>  > Ioannis
>
>
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