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43 lines
1.7 KiB
Plaintext
43 lines
1.7 KiB
Plaintext
created: 20140211171341271
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modified: 20221019081352266
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tags: Concepts Reference
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title: Macros
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type: text/vnd.tiddlywiki
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!! Introduction
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A <<.def macro>> is a named snippet of text. They are typically defined with the [[Pragma: \define]]:
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```
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\define my-macro(parameter:"Default value")
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This is the macro, and the parameter is $parameter$.
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\end
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```
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The name wrapped in double angled [[brackets|Brackets]] is used a shorthand way of [[transcluding|Transclusion]] the snippet. Such transclusions are known as <<.def "macro calls">>, and each call can supply a different set of parameters:
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```
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<<my-macro>>
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<<my-macro "The parameter">>
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```
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The parameters that are specified in the macro call are substituted for special placeholders within the snippet:
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* `$parameter-name$` is replaced with the value of the named parameter
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* `$(variable-name)$` is replaced with the value of the named [[variable|Variables]]).
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<<.from-version "5.3.0">> Macros have been [[superseded|Macro Pitfalls]] by [[Procedures]], [[Custom Widgets]] and [[Functions]] which together provide more robust and flexible ways to encapsulate and re-use code. It is now recommended to only use macros when textual substitution is specifically required.
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!! How Macros Work
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Macros are implemented as a special kind of [[variable|Variables]]. The only thing that distinguishes them from ordinary variables is the way that the parameters are handled.
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!! Using Macros
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* [[Macro Definitions]] describes how to create macros
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* [[Macro Calls]] describes how to use macros
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* [[Macro Parameter Handling]] describes how macro parameters work
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* [[Macro Pitfalls]] describes some of the pitfalls of using macros
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* [[Core Macros]] lists the built-in core macros
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