[stringtemplate-interest] ST map improvement

[Andrew Goodnough]

I like your idea that no default section means a pass-through (which
just returns the original key).  Thanks for taking a look.  I wish I
could say that I'd try to implement this for you but I'm not familiar
enough with the code.  Maybe it would be light work for you, though.  :)
 I'll take a look when I get time to see what I can come up with.

Andy

 
>>> Terence Parr <parrt at cs.usfca.edu> 01/07/06 12:41 pm >>> 

On Jan 4, 2006, at 6:57 AM, Andrew Goodnough wrote:
> In this case a default of "UNSUPPORTED_OPERATION" is fine but there 

> are other cases where I want the default to just return the key  
> value.  So if it's not in the map, just give me the original value  
> back.  Something like:
>
> opMap ::= [
>  "ADD":"ADD",
>  "CHANGE":"MODIFY",
>  "REMOVE":"DROP",
>  default:key
> ]

Interesting...what if no default meant you get the key?  Actually we  
need this to be consistent with a new syntax for map  
iteration...currently it's a braindead iterate- over- values thing:

<symbols:{s|<s.type> <s.name>}>

what if it's just text to text though?  You really want the keys so  
you can do this with the indirect field accessor:

<aMap:{key|<key> maps to <aMap.(key)>}

Actually, the key is not a "keyword" so no need to make consistent.

> or maybe even better:
>
> opMap ::= [
>  "ADD":"ADD",
>  "CHANGE":"MODIFY",
>  "REMOVE":"DROP",
>  default:<op_key()>  //where op_key() is a defined template
> ]

I like this direction.  Why not map string to arbitrary template  
(string or template name) in general?  Great idea!

> This would make the calling code more readable and concise.   
> Instead of:
>
> <if(it.operation)><opMap.(it.operation)><else><it.operation><endif>
>
> it could be:
>
> <opMap.(it.operation)>

Useful.

> Would this be helpful for anyone else?

An excellent use- case for this option.  What if you want default to  
go to nothing?  I.e., only spit something out if it's in a  
vocabulary?  Do I have a null or something?  Can't remember!

Ter
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