[exprla-devel] Re: [xpl] Adding up a list of numbers, check it out.

[reid_spencer <ras...@re...>]

--- In xpl-dev@y..., "Michael Lauzon" <ce940@f...> wrote:
This is also a good start, but the other way seemed a more promising 
way to go, using namespaces and whatnot, we don't want a lot of 
clutter around.  Please login to the groups site on eGroups, and
check 
out the two previous ideas for the XPL programs.  You may have to do
a 
view source in the message.  Also, can people of this list signup for 
xpl-wishlist?


--- In xpl@e..., Jonathan Burns <saski@w...> wrote:
> <xpl>
> 
> <comment> This line is mandatory. </comment>
> 
> <include content="xpl.dtd" version="x.x"/ >
> 
> <comment>
>     This includes a pre-existing data type,
>     an XML document with the structure
>     containing a list of integers:
> 
>     <List>
>         [ <int> string </int> ]*
>     </List>
> 
>     Within the program, an element of this form
>     will be referred to by the name "intList".
> </comment>
> 
> <include intList="list-of-int.dtd">
> 
> <comment>
>     Here we define a program variable to contain
>     a list of integers.
> <comment>
> 
> <variable type=intList>
>     <name>
>         mylist
>     </name>
> </variable>
> 
> <comment>
> 
>     We define an integer variable>
> 
> </comment>
> 
> <variable type=int>
>     <name>
>         total
>     </name>
> </variable>
> 
> <comment>
> 
>     We define a general-purpose element
> 
> </comment>
> 
> <variable type=element>
>     <name>
>         index
>     </name>
> </variable>
> 
> <comment>
> 
>     We define "abort" as a macro for an
>     action to take on error.
> 
> </comment>
> 
> <set>
>     abort
> 
>     <stdout>
>         <data>
>             <List>
>                 zero
>             </List>
>         </data>
>      </stdout>
> </set>
> 
> <comment>
> 
>     At last, the action commences!
> 
>     We read in the intList data.
> 
> </comment>
> 
> <stdin>
>     mylist
> </stdin>
> 
> <if>
>     <false>
>         <verify>
>             mylist
>         </verify>
>     </false>
> 
>     abort        <comment> Handy things, macros. </comment>
> </if>
> 
> <comment>
> 
>     We set the general element "index" to refer
>     to mylist as a whole. But we can think of this
>     as referring to the root of the mylist.
>     (Compare directory commands: think of this as
>     setting up "index" as a symbolic link to mylist.)
> 
>     N.B. "set" is used here as a full copy assignment,
>     with all children. It may be wasteful in some cases.
> 
> </comment>
> 
> <set>
>     index
>     mylist
> </set>
> 
> <comment>
> 
>     Check whether mylist is empty.
> 
> </comment>
> 
> <if>
>     <equals>
>         <number-of-children>
>             mylist
>         </number-of-children>
>         zero
>     <equals>
> 
>     abort
> 
> <else>
> 
>     <comment>
> 
>         Shift "index" down, to refer to "mylist"'s first child.
>         (Compare change-directory command.)
> 
>     </comment>
> 
>     <set>
>         index
>         <first-child>
>             index      <comment> This could as well be "mylist".
> </comment>
>         </first-child>
>     </set>
> 
>     <comment>
> 
>         Initialize our "total" variable.
> 
>     </comment>
> 
>     <set>
>         total
> 
>         <data>
>             <int>
>                 zero
>             </int>
>         <data>
>     </set>
> 
>     <comment>
> 
>         And this is what does the work:
>         a Do-While loop which adds the list elements
>         to our "total" variable.
> 
>         N.B.
>             It doesn't make sense to add up strings,
>             even strings like "9848001" and "0".
>             But it does make sense to add up elements
>             such as
> 
>                 <int>
>                     9848001
>                 </int>
> 
>     </comment>
> 
>     <do>
> 
>         <add>
>             total
>             index
>         </add>
> 
>         <comment>
> 
>             Here's the While condition
> 
>         </comment>
> 
>         <not> <equals>
>              index
>              <last-child>
>                 mylist
>              <last-child>
>          </equals>
>      </do>
> 
> </else>
> </if>
> 
> <comment>
> 
>     And we're out, with the list elements
>     added up in "total".
>     So, output it.
> 
> </comment>
> 
> <stdout>
>    <data>
>        <List>
>             total
>         </List>
>      </data>
> </stdout>
> 
> <comment>
> 
>     And take the rest of the day off.
> 
> </comment>
> 
> </xpl>
--- End forwarded message ---