I'm slowly winding my way up the learning curve by adapting Joel Dueck's
work to a personal web-book I want to write.
I've hit a snag due to my limited understanding of racket, probably.
The template.pdf.p files contains the following line to generate a nicely
formatted LaTex date:
\date{◊(pubdate->english (hash-ref metas 'doc-publish-date))}
*metas *is generated from meta values in the source files, with one of the
keys being "doc-publish-date".
*pubdate->English * is a helper function to format everything nicely.
This works perfectly if I don't forget the "doc-publish-date" key in the
source files. If I do (or don't want to set it), the *hash-ref* fails and
stops the rendering process.
The *hash-ref* documentation (hash-ref
<http://docs.racket-lang.org/reference/hashtables.html?q=hash-ref%20#%28def._%28%28quote._~23~25kernel%29._hash-ref%29%29>)
mentions
that one can write:
hash-ref hash key [failure-result]
were *failure-result* is either a procedure or is a value and gets returned
instead of the missing key-value.
I've been trying to use this in order to fail gracefully when *doc-publish-date
*is missing:
* either by returnnig a blank value (so the LaTex output will be " \date()
"
* or, even better, by skipping the whole \date function if the *hash-ref*
function fails.
Unfortunately all my efforts to set the failure-result have failed. I've
tried e.g.
\date{◊(pubdate->english (hash-ref metas 'doc-publish-date [] ))}
in order to return an empty string, but racket chokes by telling me [] is
not a procedure.
And I can't find reference to something resembling if-error in the racket
documentation.
Any pointers would be greatly appreciated!
P.
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