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TiddlyWiki5/editions/tw5.com/tiddlers/macros/syntax/Procedure Definition Syntax.tid

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created: 20240310165023000
modified: 20240310175033730
tags: [[Procedure Syntax]]
title: Procedure Definition Syntax
type: text/vnd.tiddlywiki
<<.preamble """What follows is a formal presentation of the syntax of the [[Pragma: \procedure]], using [[railroad diagrams|Railroad Diagrams]]. """>>
! \procedure
There are 2 types of procedure definitions
* Single line definitions
* Multi line definitions
!! Single Line
Single line definitions should only be used for very short bodies, where the procedure name, params and the body fit into 1 line terminated with a line-feed.
<$railroad text="""
"\procedure"
[[<"space">|"Filter Whitespace"]]
"procedure-name"
<"(params)">
[:[[<"space">|"Filter Whitespace"]]]
"body"
"lf"
"""/>
!! Multi Line
The majority of procedure definitions will have a body, that spans over several lines of wikitext. Those procedure definitions are terminated using the "\end" pragma
<$railroad text="""
"\procedure"
[[<"space">|"Filter Whitespace"]]
"procedure-name"
<"(params)">
[:[[<"space">|"Filter Whitespace"]]]
body
"\end"
"""/>
The [[procedure-name|Procedures]] is a sequence of non-whitespace characters other than `(` or `>`.
* <<.place procedure-name>> is a sequence of letters (`A`--`Z`, `a`--`z`), digits (`0`--`9`), hyphens (`-`) and underscores (`_`)
* <<.place body>> is wikitext including [[nested procedures|Pragma: \procedure]]
* <<.place space>> denotes a sequence of [[whitespace characters|Filter Whitespace]]
!! params
The parameter declaration list <<.place (params)>> has the following syntax:
<$railroad text="""
\start none
\end none
"(" [:"sep"] [:{ parameter "sep" }] ")"
"""/>
* <<.place sep>> is any sequence of characters that does not match a <<.place param-name>>. <br>Among other things, this includes commas, spaces and linefeeds.
Each ''individual'' <<.place parameter>> has the following syntax:
<$railroad text="""
\start none
\end none
"param-name" [: [:[[<"space">|"Filter Whitespace"]]] ":" [:[[<"space">|"Filter Whitespace"]]] default ]
"""/>
* <<.place param-name>> is a sequence of letters (`A`--`Z`, `a`--`z`), digits (`0`--`9`), hyphens (`-`) and underscores (`_`).
* <<.place default>> is an optional value of a parameter is specified as follows:
<$railroad text={{$:/editions/tw5.com/railroad/macro-parameter-value}}/>
!! body
The <<.place body>> of the definition has the following syntax:
<$railroad text="""
\start none
\end none
{[[<"wikitext">|WikiText]] "lf"}
"""/>
* <<.place wikitext>> is any sequence of characters that doesn't terminate the macro definition.
** If [[nested procedures|Pragma: \procedure]] are used they need to be at the start of the wikitext. There are the same rules as if the wikitext would be in a tiddler.
** Pragmas need to be before standard wikitext.
* <<.place lf>> denotes a linefeed.