What is "Open Language"?

Mark Waddingham mark at livecode.com
Tue Oct 27 05:02:59 EDT 2015

On 2015-10-25 00:19, Monte Goulding wrote:
> OK, well we can let Mark Waddingham comment on whether I’m right in
> that control structures are unlikely targets for open language or not.
> It seems quite unlikely to me as it’s significantly more complicated
> than commands. I’m not saying it’s not possible the ROI would be
> terrible. As in almost 0 return for a reasonably heavy investment…

Initially, Open Language will allow you to define:
     - commands
     - expressions
     - iterators

This is the range of things which the 'custom' LiveCode Builder syntax 
is built upon (which means I know it definitely works!).

Commands are what they you would imagine - they are a sequence of tokens 
interspersed with expressions:
     'put' <Expression> 'after' <Expression>

Expressions fall into three categories. First we have 'prefix 
     'word' <Expression> 'of' <Expression>

Then we have postfix operators:
      <Expression> 'is' 'a' 'number'

Then we have infix operators:
      <Expression> 'is' 'less' 'than' <Expression>

Then we have radical expressions:
      'the' 'empty' 'string'

Note that in all three 'operator' cases, you can also have expressions 
in-between the tokens:
      <Expression> 'is' 'between' <Expression> 'and' <Expression>

The thing which defines what class of operator it is is determined by 
whether there is an expression on the left, right or both.

Iterators are essentially extensions to 'repeat':
      'repeat' 'for' 'each' 'char' <Variable> 'in' <Expression>

Basically, we'll extend the reach of Open Language in terms of what you 
can create in the host language with it over time. Already, implementing 
the initial LiveCode Builder compiler has taught me that there need to 
be a greater set of patterns such as property accesses, chunks etc. - 
defining them at the low level 'syntax clause' point is a little too 
much work (although a great deal less then writing explicit C code as an 
ad-hoc parser in the engine ;)).

Warmest Regards,


Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps

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