Three weeks ago, I started you off on a tour of Zope Page Templates, explaining what they were and how they could make your life more interesting. I unraveled the mystery behind TAL, the attribute language used in ZPT, and TALES, the expression syntax that allows you to use TAL in a logical manner. I showed you how to place content and replace text within a template, define variables, create and use conditionals and loops, and use ZPT's error-handling capabilities
So where that does leave us? At the threshold of the concluding article of this series, in which I'll be explaining the third component of the ZPT jigsaw: METAL.
METAL, or Macro Expansion for TAL is "...an attribute language for structured macro preprocessing". Translated, this means that METAL allows you to simplify your ZPT development with macros, code snippets that can be reused extensively across one or more templates. The obvious advantage of this: a single change in the macro will be immediately visible at all places that it has been referenced.
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