[Zope] MetaPublisher and dtml-let

[Stephan Goeldi]

What is wrong with this construct?

<dtml-let a="mp_entries.getEntryField(_['key'],'f1071131972')"
          b="mp_entries.getEntryField(_['key'],'f1071139087')"
          c="a*b"

   <dtml-var c>

</dtml-let>


I get this Zope Error:
Error Type: TypeError
Error Value: unsupported operand type(s) for *

a and b are both float variables.

Traceback (innermost last):

      * Module ZPublisher.Publish, line 49, in publish
      * Module ZPublisher.mapply, line 32, in mapply
      * Module ZPublisher.Publish, line 38, in call_object
      * Module OFS.DTMLDocument, line 102, in __call__
      * Module DocumentTemplate.DT_String, line 361, in __call__
      * Module DocumentTemplate.DT_Let, line 70, in render
      * Module DocumentTemplate.DT_Util, line 175, in eval
        __traceback_info__: a
      * Module <string>, line 2, in f
      * 
      *