350 lines
4.6 KiB
Plaintext
350 lines
4.6 KiB
Plaintext
created: 20150103184022184
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modified: 20150119220342000
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title: $:/plugins/tiddlywiki/railroad/syntax
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The railroad widget uses a special notation to construct the components defined below.
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`x` and `y` here stand for any component.
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Names (as opposed to quoted strings) are available when a value starts with a letter and contains only letters, digits, underscores, dots and hyphens.
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---
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; sequence
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: <$railroad text=""" ["<-"] {x} ["->"] """/>
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* A sequence of components
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* The `<-` and `->` delimiters allow you to force a single component to be treated as a sequence. This is occasionally useful for spacing a diagram out
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examples
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<<<
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```
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x y z sequence
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```
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<$railroad text=""" x y z """/>
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```
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<-x y z-> explicit sequence
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```
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<$railroad text=""" <- x y z -> """/>
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<<<
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---
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; optional
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: <$railroad text=""" "[" [":"] x "]" """/>
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* A component that can be omitted
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* The colon makes `x` appear straight ahead
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examples
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<<<
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```
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[:x] optional, normally included
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```
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<$railroad text=""" [:x] """/>
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```
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[x] optional, normally omitted
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```
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<$railroad text=""" [x] """/>
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<<<
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---
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; repeated
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: <$railroad text=""" "{" x [:"+" y] "}" """/>
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* A list of one or more `x`
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* The `+` suffix adds `y` as a separator between each `x` and the next
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examples
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<<<
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```
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{x} one or more
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```
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<$railroad text=""" {x} """/>
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```
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{x +","} one or more, comma-separated
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```
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<$railroad text=""" {x +","} """/>
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<<<
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---
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; optional repeated
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: <$railroad text=""" "[{" [":"] x [:"+" y] "}]" """/>
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* An optional list of `x`, i.e. a list of zero or more `x`
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examples
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<<<
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```
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[{:x}] zero or more, normally included
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```
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<$railroad text=""" [{:x}] """/>
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```
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[{:x +","}] zero or more, comma-separated, normally included
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```
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<$railroad text=""" [{:x +","}] """/>
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```
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[{x}] zero or more, normally omitted
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```
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<$railroad text=""" [{x}] """/>
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```
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[{x +","}] zero or more, comma-separated, normally omitted
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```
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<$railroad text=""" [{x +","}] """/>
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<<<
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---
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; choice
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: <$railroad text=""" "(" {[:":"] x +"|"} ")" """/>
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* A set of alternatives
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* The colon indicates which branch appears straight ahead. By default, it's the first branch
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examples
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<<<
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```
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(x|y|z) alternatives
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```
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<$railroad text=""" (x|y|z) """/>
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```
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(x|:y|z) alternatives, normally y
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```
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<$railroad text=""" (x|:y|z) """/>
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<<<
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---
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; string / terminal
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: <$railroad text={{$:/plugins/tiddlywiki/railroad/syntax-string}}/>
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* A literal or terminal component
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* This follows the normal ~TiddlyWiki rules for quoted strings
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examples
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<<<
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```
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"x" terminal
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```
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<$railroad text=""" "x" """/>
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<<<
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---
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; nonterminal
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: <$railroad text=""" (name | "<" string ">") """/>
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* A nonterminal component, i.e. the name of another diagram
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examples
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<<<
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```
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<"x"> nonterminal
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```
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<$railroad text=""" <"x"> """/>
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<<<
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---
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; comment
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: <$railroad text=""" "/" string "/" """/>
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* A comment
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examples
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<<<
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```
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/ "comment" / comment
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```
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<$railroad text=""" / "comment" / """/>
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<<<
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---
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; dummy
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: <$railroad text=""" "-" """/>
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* The absence of a component
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examples
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<<<
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```
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- dummy
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```
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<$railroad text=""" - """/>
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<<<
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---
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; link
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: <$railroad text=""" "[[" x "|" (name|string) "]]" """/>
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* A link to the tiddler title or URI given by the string or name
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examples
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<<<
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```
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[[x|"tiddler"]] link
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```
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<$railroad text=""" [[x|"tiddler"]] """/>
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<<<
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---
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; transclusion
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: <$railroad text=""" "{{" (name|string) "}}" """/>
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* Treats the content of another tiddler as diagram syntax and transcludes it into the current diagram
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examples
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<<<
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```
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{{"$:/plugins/tiddlywiki/railroad/example-transclusion"}} transclusion
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// "railroad transclusion example" text <- text in the tidlder
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```
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<$railroad text=""" {{ "$:/plugins/tiddlywiki/railroad/example-transclusion" }} """/>
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<<<
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---
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; arrow pragma
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: <$railroad text=""" "\arrow" ("yes" | "no") """/>
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* Controls whether repeat paths have an arrow on them
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* Can be toggled on and off in mid-diagram, if desired
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examples
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<<<
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```
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<$railroad text="""
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\arrow yes
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[{:x}]
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"""/>
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```
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<$railroad text="""\arrow yes [{:x}] """/>
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```
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<$railroad text="""
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\arrow no
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[{:x}]
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"""/>
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```
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<$railroad text="""\arrow no [{:x}] """/>
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<<<
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---
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; debug pragma
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: <$railroad text=""" "\debug" """/>
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* Causes the diagram to display its parse tree
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examples
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<<<
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```
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\debug
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x
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```
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<$railroad text="""\debug x """/>
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<<<
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---
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; start/end pragma
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: <$railroad text=""" ("\start" |: "\end") ("none" |: "single" | "double") """/>
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* Controls the style of the diagram's startpoint or endpoint
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examples
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<<<
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```
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\start none x
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```
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<$railroad text=""" \start none x """/>
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```
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\start double
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\end double
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x
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```
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<$railroad text=""" \start double
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\end double
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x
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"""/>
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<<<
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