[Ur] Simple XML Templating Problem

Thu Oct 2 16:26:25 EDT 2014

More growing pains.  I've taken my example a bit further to:

style footer
style header

fun head_tmpl (_title:string) =
    <xml><head><title>{[_title]}</title></head></xml>

fun header_tmpl () : xbody = <xml><div class="header">header</div></xml>
fun footer_tmpl () : xbody = <xml><div class="footer">footer</div></xml>

fun body_tmpl (body_xml:xbody) =
    <xml><body>
    {header_tmpl ()}
    {body_xml}
    {footer_tmpl ()}
    </body></xml>

fun page (title:string, body:xbody) =
    <xml>
    {head_tmpl title}
    {body_tmpl body}
    </xml>

fun main () : transaction page =
    return (page "BlogMain" <xml/>)

There's a problem with the main function even with the type decleration:

urweb blog
/home/burton/blog/blog.ur:24:17: (to 24:27) Unification failure
Expression:  "BlogMain"
  Have con:  string
  Need con:
string * (xml ([Dyn = (), MakeForm = (), Body = ()]) ([]) ([]))
Incompatible constructors
Have:  string
Need:
string * (xml ([Dyn = (), MakeForm = (), Body = ()]) ([]) ([]))
/home/burton/blog/blog.ur:24:12: (to 24:27) Unification failure
Expression:  page "BlogMain"
  Have con:  xml ([Html = ()]) ([]) ([])
  Need con:  <UNIF:U344::Type> -> <UNIF:U345::Type>
Incompatible constructors
Have:  xml ([Html = ()]) ([]) ([])
Need:  <UNIF:U344::Type> -> <UNIF:U345::Type>

Still learning the basics but I think once I get over the learning curve
things will go a quite a bit smoother.

--
Burton Samograd

On Thu, Oct 2, 2014 at 1:56 PM, Sergey Mironov <grrwlf at gmail.com> wrote:

> 2014-10-02 23:33 GMT+04:00 Burton Samograd <burton.samograd at gmail.com>:
> > Still no luck:
> >
> > fun head_template (_title:string) =
> >     return <xml><head><title>{[_title]}</title></head></xml>
> >
> > fun main () = return <xml>
> >     {head_template "Blog Main"}
> >     <body>
> >     </body>
> >     </xml>
>
> The error is caused by the type mismatch. <xml>{f x}</xml> works only
> for pure functions f. Pure functions usually don't mention
> 'transaction' in their type signatures, nor they use 'return' keyword
> in their bodies. Your code snippet have two problems: 1) unspecified
> type for [main] and 2) 'return' keyword in [head_template] conflicting
> with <xml>{..}</xml> call. Try this code instead:
>
>  fun head_template (_title:string) =
>      <xml><head><title>{[_title]}</title></head></xml>
>
>  fun main () : transaction page = return <xml>
>      {head_template "Blog Main"}
>      <body>
>      </body>
>      </xml>
>
> Regards,
> Sergey
>
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