Re: How do you create a grammar for a multi-language language?

> I am working with a team to develop a new language and our current thinking is
> that the language will use the XPath language for navigating through documents
> and the CSS language for expressing sets of match/action pairs.


That feels like a much more tractable problem. Don't even think of it
as a multi-language language. It's a language you're designing (so you
have lots of room for maneuver) around XPath.


> This idea of multi-language languages is very common within the XML community.
> For example, the XSLT language uses (hosts) the XPath language. Here is an
> excerpt to illustrate:
>
> select="/Bookstore/Book[1]/Title"
>
> The expression /Bookstore/Book[1]/Title is an XPath expression, the other
> parts are XSLT. So, the format of the select statement is:
>
> select="XPath"
>
> See how XSLT hosts XPath? That is, one language (XSLT) is using another
> language (XPath).


Yeah, putting a second language inside the string literals of the
first is a very common approach. All the tooling for the outer
language can remain oblivious of the second. You don't even need to
design a new language, this approach works with any existing one, and
you can focus on implementing a library to process XPath.


If you do want to design another language, however, you can make things a lot nicer. For example:


- any URL is a valid literal in the Red programming language: https://github.com/red/docs/blob/master/en/datatypes.adoc
- the JSX extension of JavaScript used in the React framework permits component literals that look a lot like some sort of markup language: https://reactjs.org/docs/introducing-jsx.html


Kartik
http://akkartik.name/about

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