On Aug 1, 2016, at 12:43 PM, Chris Forster <[email protected]> wrote:
>
> (txexpr 'div '((id "top")) '("Hello" (p "World")))
>
> I'm not sure I understand why the nested paragraph wouldn't also be a
> txexper--would there ever be a situation where the following would make sense?
>
> (txexpr 'div '((id "top")) '("Hello" (txexpr 'p empty "World")))
>
True, the second expression will test as a `txexpr?`, but notice that it's not
giving the result you expect:
'(div ((id "top")) "Hello" (txexpr 'p empty "World")) ; wrong!
Because '("Hello" (txexpr 'p empty "World")) is prefixed with a quote,
everything inside gets quoted, including the `txexpr`. Instead, you could do
this:
(txexpr 'div '((id "top")) `("Hello" ,(txexpr 'p empty '("World"))))
Now, this expression will have the same result as:
(txexpr 'div '((id "top")) '("Hello" (p "World")))
>
> Likewise, if I follow, does that mean that there is no situation where a
> txexper can't be replaced by a quasiquoted expression?
Right. A txexpr is just a Racket list, with some special conditions about what
values can appear where. In general, you can use any of Racket's list-making /
list-breaking functions to make a txexpr. Quasiquoting is just a way of making
a list. The advantage of the `txexpr` function itself is that it will check
your arguments to make sure they will result in a valid txexpr. Sometimes
that's helpful. Sometimes not.
In the `pollen-tfl` docs I show some examples of how different Racket functions
can make valid txexprs:
http://docs.racket-lang.org/pollen-tfl/_pollen_rkt_.html#%28part._.Making_tagged_.X-expressions__txexprs_%29
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