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Fixes PR12767

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This commit is contained in:
Jay McCarthy 2012-06-07 13:42:46 -06:00
parent 41a890df03
commit 6db5672ac5
1 changed files with 14 additions and 12 deletions
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26
collects/web-server/scribblings/tutorial/continue.scrbl
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@ -214,22 +214,24 @@ another list that acts as a template. For example, given the list of
@|xexpr|s @racket['((li "Larry") (li "Curly") (li "Moe"))], we may want
to create the single @|xexpr|
@racket['(ul (li "Larry")
(li "Curly")
(li "Moe"))]
@racketblock[
'(ul (li "Larry")
(li "Curly")
(li "Moe"))
]
This can't be done using plain unquoting, because placing a comma in front of
@racket['("Larry" "Curly" "Moe")] will unquote the entire list, yielding
the malformed expression @racket['(ul ((li "Larry") (li "Curly") (li
This can't be done using plain unquoting, because placing a comma in
front of @racket['((li "Larry") (li "Curly") (li "Moe"))] will unquote
the entire list, yielding the malformed expression
@racket['(ul ((li "Larry") (li "Curly") (li
"Moe")))].
Instead, we must splice the list in, like so: @racket[`(ul ,@((li "Larry") (li "Curly") (li
"Moe")))]. The unquote-splicing form, @racket[,@expression],
allows us conveniently to splice a list of @|xexpr| fragments into a
larger template list. To generalize
the example, here are two helper functions that convert any list of
@|xexpr|s into one
@|xexpr| representing an unordered, itemized HTML list:
larger template list. To generalize the example, here are two helper
functions that convert any list of @|xexpr|s into one @|xexpr|
representing an unordered, itemized HTML list:
@racketblock[
@code:comment{render-as-itemized-list: (listof xexpr) -> xexpr}
@ -273,8 +275,8 @@ should produce
@racketblock[
'(div ((class "posts"))
(div ((class "post")) "Post 1" "Body 1")
(div ((class "post")) "Post 2" "Body 2"))
(div ((class "post")) "Post 1" (p "Body 1"))
(div ((class "post")) "Post 2" (p "Body 2")))
]
@centerline{------------}