Re: Encoding reserved characters in URI query strings

[Aditya Mahajan <adityam@umich.edu>]

On Sun, 5 Feb 2017, Rogers, Michael K wrote:

> Let's say I want a link to plot x+2 in Wolfram|Alpha.  I need to catenate "http://www.wolframalpha.com/input/?i=" and  "plot+x%2B2".  Is there any way already available in ConTeXt to translate reserved characters like "+" to the percent-hexcode "%2B"?
>
> Something like
>
>    \encode[plot x+2]
>
> would become
>
>    plot+x%2B2
>
> Or more generally, some languages have a query constructor like this
>
>    \queryURI
>      [http://www.wolframalpha.com/input]
>      [i=plot x+2]
>
> which would construct the URI
>
>    http://www.wolframalpha.com/input/?i=plot+x%2B2
>
> I could write my own, of course.  But no need to reinvent the wheel.

url.escape does exactly that.

\startluacode
   local base="http://www.wolframalpha.com/input"
   local query="i=plot x+2"
   local fullname = base .. query
   print(url.escape(fullname))
\stopluacode

gives

http%3A//www.wolframalpha.com/inputi%3Dplot%20x%2B2

Also look at l-url.lua for other helper functions for parsing and 
escaping/unescaping urls.

Aditya
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