@ -31,7 +31,7 @@ You can retrieve a meta value —even in the same document where you define it
@section{Splicing}
@defform[(\@ arg ...)]
Splicing tag: signals that a list should be merged into its containing expression. The splicing tag is @racket[setup:splicing-tag].
The splicing tag signals that a list should be merged into its containing expression. The splicing tag is @racket['\@].
@examples[#:eval my-eval
(module splicer pollen/markup
@ -40,6 +40,24 @@ Splicing tag: signals that a list should be merged into its containing expressio
doc
]
The splicing tag is useful when you want to return a list of X-expressions in a situation where you can only return one. For instance, @secref["Tag_functions"] can only return one X-expression. But if we wrap the list of X-expressions in a splicing tag, they behave like a single X-expression. Later, Pollen will merge the list elements into the surrounding expression (as shown above).
@examples[#:eval my-eval
(require pollen/tag)
(code:comment @#,t{wrong: function returns a list of X-expressions})
(define-tag-function (multi attrs elems)
'("foo" "bar"))
(code:comment @#,t{right: function returns a list of X-expressions})
(code:comment @#,t{as elements inside a splicing tag})
(define-tag-function (multi2 attrs elems)
'(\@ "foo" "bar"))
]
Though the splicing tag is cosmetically identical to the abbreviated notation of @litchar{@"@"} for @racket[unquote-splicing], and has a similar purpose, it's not the same thing. The splicing tag isn't a variable —it's just a symbol that Pollen treats specially when generating output.
@defform[(when/splice condition pollen-args)]
If @racket[_condition] is true, put the @racket[_pollen-args] into the document. Within a template file, usually invoked like so:
