@ -112,6 +112,15 @@ Note that if @racket[_meta-source] is a relative path or pagenode, it is treated
]
]
@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:
@verbatim{◊when/splice[@racketvarfont{condition}]{The text to insert.}}
The inserted text can contain its own nested Pollen commands.
@racket[when/splice] can be more convenient than @racket[when], because @racket[when] will only use the last argument between the curly braces. @racket[when/splice], by contrast, treats everything between the curly braces as a block.
@ -672,7 +672,7 @@ One way to fix the problem would be to have three separate template files —t
But since we have a whole programming language available in Pollen, that's a dull-witted way to solve the problem. The better way is to add @italic{conditionals} to the template to selectively change the navigation. That keeps things simple, because we'll still have only one @filepath{template.html} to deal with.
But since we have a whole programming language available in Pollen, that's a dull-witted way to solve the problem. The better way is to add @italic{conditionals} to the template to selectively change the navigation. That keeps things simple, because we'll still have only one @filepath{template.html} to deal with.
To handle @filepath{article.html}, we want to hide the previous-page navigation link when there's no previous page. As it turns out, if the @racket[previous] function can't find a previous page, it will return false. So we just need to wrap our previous-page navigation in the @racket[when/block] command like so:
To handle @filepath{article.html}, we want to hide the previous-page navigation link when there's no previous page. As it turns out, if the @racket[previous] function can't find a previous page, it will return false. So we just need to wrap our previous-page navigation in the @racket[when/splice] command like so:
@fileblock["template.html"
@fileblock["template.html"
@codeblock[#:keep-lang-line? #f]{
@codeblock[#:keep-lang-line? #f]{
@ -685,14 +685,14 @@ To handle @filepath{article.html}, we want to hide the previous-page navigation
The next is <a href="◊|(next here)|">◊|(next here)|</a>.
The next is <a href="◊|(next here)|">◊|(next here)|</a>.
</body>
</body>
</html>
</html>
}]
}]
The basic structure of @racket[when/block] is @tt{◊when/block[@racketvarfont{condition}]{@racketvarfont{insert-this-text}}.} Note the square braces around the @racketvarfont{condition}, and the curly braces around the @racketvarfont{text}. Using @racket[(previous here)] as the condition is shorthand for ``when @racket[(previous here)] does not return false...''
The basic structure of @racket[when/splice] is @tt{◊when/splice[@racketvarfont{condition}]{@racketvarfont{insert-this-text}}.} Note the square braces around the @racketvarfont{condition}, and the curly braces around the @racketvarfont{text}. Using @racket[(previous here)] as the condition is shorthand for ``when @racket[(previous here)] does not return false...''
Programmers in the audience might be getting anxious about the repeated use of @racket[(previous here)] — you're welcome to store that value in a variable, and everything will work the same way:
Programmers in the audience might be getting anxious about the repeated use of @racket[(previous here)] — you're welcome to store that value in a variable, and everything will work the same way:
@ -708,7 +708,7 @@ Programmers in the audience might be getting anxious about the repeated use of @
<body>◊->html[doc]
<body>◊->html[doc]
The current page is called ◊|here|.
The current page is called ◊|here|.
◊(define prev-page (previous here))
◊(define prev-page (previous here))
◊when/block[prev-page]{The previous is
◊when/splice[prev-page]{The previous is
<a href="◊|prev-page|">◊|prev-page|</a>.}
<a href="◊|prev-page|">◊|prev-page|</a>.}
The next is <a href="◊|(next here)|">◊|(next here)|</a>.
The next is <a href="◊|(next here)|">◊|(next here)|</a>.
</body>
</body>
@ -717,7 +717,7 @@ The next is <a href="◊|(next here)|">◊|(next here)|</a>.
We need a different technique for handling the end of the next-page navigation, because we're not reaching the actual end of the pagetree. We're just reaching the end of the pages we care about navigating through.
We need a different technique for handling the end of the next-page navigation, because we're not reaching the actual end of the pagetree. We're just reaching the end of the pages we care about navigating through.
What condition will help us detect this? Here, we can notice that the names of our article pages all contain the string @code{article}. While you'd probably want a more robust condition for a real project, in this tutorial, what we'll do is hide the next-page navigation if the name of the next page doesn't contain ``@code{article}''. As we did before, we wrap our navigation line in the @racket[when/block] function:
What condition will help us detect this? Here, we can notice that the names of our article pages all contain the string @code{article}. While you'd probably want a more robust condition for a real project, in this tutorial, what we'll do is hide the next-page navigation if the name of the next page doesn't contain ``@code{article}''. As we did before, we wrap our navigation line in the @racket[when/splice] function:
@fileblock["template.html"
@fileblock["template.html"
@codeblock[#:keep-lang-line? #f]{
@codeblock[#:keep-lang-line? #f]{
@ -731,9 +731,9 @@ What condition will help us detect this? Here, we can notice that the names of o
@ -954,7 +954,7 @@ This page isn't a miracle of web design, but it shows you in one example:
@item{A dynamically-generated CSS file that computes positions for CSS elements using numerical values set up with @racket[define], and mathematical conversions thereof;}
@item{A dynamically-generated CSS file that computes positions for CSS elements using numerical values set up with @racket[define], and mathematical conversions thereof;}
@item{Navigational links that appear and disappear as needed using conditional statements (@racket[when/block]) in @filepath{template.html}, with the page sequence defined by @filepath{index.ptree} and the names of the links being pulled from the @code{h1} tag of each source file using @racket[select].}
@item{Navigational links that appear and disappear as needed using conditional statements (@racket[when/splice]) in @filepath{template.html}, with the page sequence defined by @filepath{index.ptree} and the names of the links being pulled from the @code{h1} tag of each source file using @racket[select].}
@ -155,6 +155,9 @@ Default separators used in decoding. The first two are initialized to @racket["\
@defoverridable[here-path-key symbol?]{Key used to store the absolute path of the current source file in its @racket[metas] hashtable. Default is @racket['here-path].}
@defoverridable[here-path-key symbol?]{Key used to store the absolute path of the current source file in its @racket[metas] hashtable. Default is @racket['here-path].}
@defoverridable[splicing-tag symbol?]{Key used to signal that an X-expression should be spliced into its containing X-expression. Default is @val[world:splicing-tag].}
@defoverridable[poly-source-ext symbol?]{Extension that indicates a source file can target multiple output types. Default is @racket['poly].}
@defoverridable[poly-source-ext symbol?]{Extension that indicates a source file can target multiple output types. Default is @racket['poly].}
