[Zope] The Zope Book - a problem with example.

[infotechsys]

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Hi,
I'm trying to learn Zope by doing the examples
in the Zope book. I'm having a bit of a problem
with the example on page 41 and 42. The problem
is in the DTML method interestRateDisplay.
The error message said I have a bad parameter,
but I can find is for the life of me. Here's the error-

invalid parameter: "= "calculateCompoundingInterest(principal, 
interest_rate, periods, years)"", for tag <dtml-var expr= 
"calculateCompoundingInterest(principal, interest_rate, periods, years)" 
 >, on line 5 of interestRateDisplay

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Traceback (innermost last):
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/ZPublisher/Publish.py, line 150, in publish_module
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/ZPublisher/Publish.py, line 114, in publish
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/Zope/__init__.py, line 159, in zpublisher_exception_hook
    (Object: interestRateDisplay)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/ZPublisher/Publish.py, line 98, in publish
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/ZPublisher/mapply.py, line 88, in mapply
    (Object: manage_edit)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/ZPublisher/Publish.py, line 39, in call_object
    (Object: manage_edit)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/OFS/DTMLMethod.py, line 254, in manage_edit
    (Object: interestRateDisplay)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/DocumentTemplate/DT_String.py, line 320, in munge
    (Object: interestRateDisplay)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/DocumentTemplate/DT_String.py, line 340, in cook
    (Object: interestRateDisplay)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/DocumentTemplate/DT_String.py, line 177, in parse
    (Object: interestRateDisplay)
  File /usr/local/Zope-2.5.1-linux2-x86/lib/python/DocumentTemplate/DT_String.py, line 58, in parse_error
    (Object: interestRateDisplay)
Document Template Parse Error: (see above)




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