PXSL Ask-a-Question

How do you think that PXSL ought to handle tabs?

Cygwin

expand -4 tabs.txt > no-tabs.txt

Or, more to the point:

expand -4 myfile.pxsl | pxslcc > myfile.xml

Nevertheless, I still recommend not having any tabs in your source files because tabs are fragile, fickle things.

PXSL is very very well done. Quite aside from the fact that XSLT is finally somewhat readable, the fact that you've added a serious macro system means that some serious scripting of XML can occur. I'm very impressed. So far I've been able to do everything I try to do -- except one thing.

To wit: I would like to have a macro such that:

,command c a1 a2 a3

produces

<a href="c?a1=,a1&a2=,a2&a3=a3">,BODY</a>

In other words I would like to have macro parameters appear in an attribute

However I can't find a way to do it. The '-attribute=' syntax binds too tightly, and there's nothing I can pass to -href= that doesn't instantly get treated as a single string. The closest I've gotten is:

,command c a1 a2 a3 = a -href=<( ,command <<?a1=>> a1 <<&a2=>> a2 <<&a3=>> a3 )>

which for ',command -a1=s1 -a2=s2 -a3=s3' at least produces '<a href="command">' But that's it. Can't get past the first string.

I imagine the current implementation cannot do what I'm trying to do. But do you see the utility of it?

Thanks for any help. And thanks muchly for a very nice tool.

Second, good question. And, I have the answer you are looking for: Yes, you can do this in stock PXSL. The key is to remember that the <( )> delimiters open a full pxsl-fragment, which lets you include any number of statements into an argument value. The results of the statements are concatenated to yield the final argument value.

With that in mind, here's one solution:

,command c a1 a2 a3 =
  a -href=<( ,c
             <<?a1=>>
             ,a1
             <<&a2=>>
             ,a2
             <<&a3=>>
             ,a3      )>
    ,BODY
,command cmd param1 param2 param3
  <<My command link>>

which produces the following output when processed with pxslcc -i:

<a href="cmd?a1=param1&a2=param2&a3=param3">My command link</a>

Strictly speaking, we ought to rewrite the above output so that bare ampersands don't appear in the CDATA value of the href attribute:

<a href="cmd?a1=param1&amp;a2=param2&amp;a3=param3">My command link</a>

While ampersands are fine in URLs, they ought not to appear unescaped in URLs placed inside of attribute values. Fortunately, we can use PXSL's <{ }> delimiters to take care of the escaping for us automatically.

Also, to make the code's workings a little more obvious, we could factor out the portion that builds the argument body and compact the lines where the arguments' names and values are joined. Thus we end up with the following, final version of our macro:

,command c a1 a2 a3 =
  a -href=<(,hrefval)>
    ,BODY
  # build href value from arguments
  ,hrefval =
    ,c
    <{?a1=}> ,a1
    <{&a2=}> ,a2
    <{&a3=}> ,a3

I'm developing a tool which parses XML to create Swing users interfaces.

I converted some of my files from XML to PXSL and the readability was much improved.

I'm looking forward to playing with the macro system.

Thanks.

After you use it for a while, please let me know what you think, good or bad. If you find anything confusing, let me know. If the docs are hard to understand, let me know. If you have any suggestions for improvement, please let me know.

Cheers,
Tom

I have a question:

How can I pass a sequence of one or more attribute name-value-pairs to a macro? I imagine that I might want something like a varargs macro.

Thanks again.

I'd like to be able to have (something like, modulo markup) this:

,defs = -a=b -c=d -e=f ...

foo ,defs -test=true

compile to:

<foo a="b" c="d" e="f" ? test="true"/>

Thanks.

Let me think about the options.

That's what I thought.

It's a "would be nice to have" rather than a "must have" for me.

I have uploaded a quick-fix version 0.9.2 (source and RPMs) that should fix the problem. Please let me know if you have any difficulties with it.