►Pollen:   the book is a program
▼14 Module reference
14.1 Cache
14.2 Core
14.3 Decode
14.4 File
14.5 Pagetree
14.6 Render
14.7 Setup
14.8 Tag
14.9 Template
14.10 Top
►14.9 Template
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14.9.1 HTML
->html
7.7
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14.9 Template

 (require pollen/template) package: pollen

Convenience functions for templates. These are automatically imported into the eval environment when rendering with a template (see render).

14.9.1 HTML

 (require pollen/template/html) package: pollen

Functions specific to HTML templates.

procedure

(->html xexpr-or-xexprs    
  [#:tag html-tag    
  #:attrs html-attrs    
  #:splice? splice-html?]) → string?
  xexpr-or-xexprs : (or/c xexpr? (listof xexpr?))
  html-tag : (or/c #f txexpr-tag?) = #f
  html-attrs : (or/c #f txexpr-attrs?) = #f
  splice-html? : boolean? = #f
Convert xexpr-or-xexprs to an HTML string. Similar to xexpr->string, but consistent with the HTML spec, text that appears within script or style blocks will not be escaped.

Examples:
> (define tx '(root (script "3 > 2") "Why is 3 > 2?"))
> (xexpr->string tx)

"<root><script>3 &gt; 2</script>Why is 3 &gt; 2?</root>"

> (->html tx)

"<root><script>3 > 2</script>Why is 3 &gt; 2?</root>"

The optional keyword arguments html-tag and html-attrs let you set the outer tag and attributes for the generated HTML. If xexpr-or-xexprs already has an outer tag or attributes, they will be replaced.

Examples:
> (define tx '(root ((id "huff")) "Bunk beds"))
> (->html tx)

"<root id=\"huff\">Bunk beds</root>"

> (->html tx #:tag 'div)

"<div id=\"huff\">Bunk beds</div>"

> (->html tx #:attrs '((id "doback")))

"<root id=\"doback\">Bunk beds</root>"

> (->html tx #:tag 'div #:attrs '((id "doback")))

"<div id=\"doback\">Bunk beds</div>"

Whereas if xexpr-or-xexprs has no tag or attributes, they will be added. If you supply attributes without a tag, you’ll get an error.

Examples:
> (define x "Drum kit")
> (->html x)

"Drum kit"

> (->html x #:tag 'div)

"<div>Drum kit</div>"

> (->html x #:tag 'div #:attrs '((id "doback")))

"<div id=\"doback\">Drum kit</div>"

> (->html x #:attrs '((id "doback")))

->html: contract violation

  expected: can't use attribute list without a #:tag

argument

  given: #f

If the generated HTML has an outer tag, the splice-html? option will strip it off. Otherwise this option has no effect.

Examples:
> (define tx '(root (p "Chicken nuggets")))
> (->html tx)

"<root><p>Chicken nuggets</p></root>"

> (->html tx #:splice? #t)

"<p>Chicken nuggets</p>"

> (define x "Fancy sauce")
> (->html x)

"Fancy sauce"

; This next one won't do anything
> (->html x #:splice? #t)

"Fancy sauce"

; Adds the outer tag, but then #:splice? removes it
> (->html x #:tag 'div #:attrs '((id "doback")) #:splice? #t)

"Fancy sauce"

Be careful not to pass existing HTML strings into this function, because the angle brackets will be escaped. Fine if that’s what you want, but you probably don’t.

Examples:
> (define tx '(p "You did " (em "what?")))
> (->html tx)

"<p>You did <em>what?</em></p>"

> (->html (->html tx))

"&lt;p&gt;You did &lt;em&gt;what?&lt;/em&gt;&lt;/p&gt;"

As the input contract suggests, this function can take either a single xexpr? or a list of xexpr?, with the expected results.

Examples:
> (define tx '(p "You did " (em "what?")))
> (->html tx)

"<p>You did <em>what?</em></p>"

> (define txs '("You " "did " (em "what?")))
> (->html txs)

"You did <em>what?</em>"

> (->html #:tag 'p txs)

"<p>You did <em>what?</em></p>"

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