On 01/28/2015 05:38 PM, Stefan Scott Alexander wrote:
On a related note:
Is it even considered "good practice" to take a function which returns
a page, and attempt to modify it by (first "unrwapping" it and then)
appending another fragment of xml to it (and then "rewrapping" it into
a [transaction page] again)?
No, there is no precedent to make that design style idiomatic. Of
course, there isn't so much Ur/Web code in the world now, so there isn't
much precedent, period!
I do think there's something fishy even about the original program
you're building on, so you should probably be evaluating the whole
approach from first principles.
For example, given a page [pg], it tries to output another page made
up of: an empty <head/> tag, with the "unwrapped" [pg] appended to it.
What if [pg] itself had a head tag?
I remember some framework I was studying was "smart" enough, when
joining <xml> fragments, to "merge" all the the content of their
<head> tags into a *single* <head> tag - but I can't remember if that
framework was UrWeb (maybe it was Yesod? :-).
Ur/Web doesn't do any HTML merging of that kind.
P.S.: I don't think it's helpful to keep mentioning the notion of
"unwrapped" in contexts like this. To me it comes across like a Java
programmer making a big deal out of the fact that a particular variable
is used as an operand to the "plus" operator.
Typed-functional-programming types think of that kind of plumbing as too
obvious to call for explicit mention.
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