57 lines
1.9 KiB
Plaintext
57 lines
1.9 KiB
Plaintext
created: 20150220200255000
|
|
modified: 20150221222349000
|
|
tags: [[Macro Syntax]] $:/deprecated
|
|
title: Macro Definition Syntax
|
|
type: text/vnd.tiddlywiki
|
|
|
|
<<.deprecated-since "5.3.0" "Procedure Definition Syntax">>
|
|
|
|
----------
|
|
|
|
<<.preamble """What follows is a formal presentation of the syntax of the `\define` pragma, using [[railroad diagrams|Railroad Diagrams]]. A [[simpler overview|Macro Definitions in WikiText]] is also available.""">>
|
|
|
|
<$railroad text="""
|
|
"\define" space name params [:space] rest
|
|
"""/>
|
|
|
|
<<.place space>> denotes a sequence of [[whitespace characters|Filter Whitespace]].
|
|
|
|
The [[macro|Macros]]'s <<.place name>> is a sequence of non-whitespace characters other than `(` or `>`.
|
|
|
|
The parameter declaration list (<<.place params>>) has the following syntax:
|
|
|
|
<$railroad text="""
|
|
"(" [:sep] [:{ param sep }] ")"
|
|
"""/>
|
|
|
|
The parameter separator (<<.place sep>>) is any sequence of characters that does not match a <<.place param-name>>. Among other things, this includes commas, spaces and linefeeds.
|
|
|
|
A <<.place param-name>> is a sequence of letters (`A`--`Z`, `a`--`z`), digits (`0`--`9`), hyphens (`-`) and underscores (`_`).
|
|
|
|
Each individual <<.place param>> has the following syntax:
|
|
|
|
<$railroad text="""
|
|
param-name [: [:space] ":" [:space] default ]
|
|
")"
|
|
"""/>
|
|
|
|
The optional <<.place default>> value of a parameter is specified as follows:
|
|
|
|
<$railroad text={{$:/editions/tw5.com/railroad/macro-parameter-value}}/>
|
|
|
|
The <<.place rest>> of the definition has the following syntax:
|
|
|
|
<$railroad text="""
|
|
( snippet | lf snippet lf "\end" [:space] ) lf
|
|
"""/>
|
|
|
|
<<.place lf>> denotes a linefeed.
|
|
|
|
The <<.place snippet>> is any sequence of characters that doesn't terminate the macro definition. That is to say, a single-line snippet cannot contain a linefeed, and a multi-line snippet cannot contain `\end` on a line of its own.
|
|
|
|
The snippet can contain placeholders with the following syntax:
|
|
|
|
<$railroad text="""
|
|
( "$" name "$" | "$" "(" name ")" "$" )
|
|
"""/>
|