Proposal: Embedded Expressions for String Statements

[Stefan Schulz]

In the light of the discussions on how to markup embedded expressions, 
it seems a really good idea to introduce a new form of String 
expressions (e.g. using a back-tick or triple-quotes as delimiter), 
which captures embedded expressions and "escape-free" and multiline 
Strings at the same time. For example by having ${ as new escape 
sequence introducing embedded expressions and $\ to introduce escape 
characters (where $\{ would escape from embedded expressions, $\\ from 
escape characters and, e.g., $\n would be a line break). I'm not sure 
about the $foo form, though.
While it seems to require more characters now for escaping, the chances 
are quite high that the two sequences ${ and $\ are rare in normal text 
and the common sequences \n and \t can be replaced by using the 
multiline feature.
It requires a bit more on pre-scanning the code, but this is only at 
compile-time when transforming the new String to old String, I think.

Stefan

John Rose schrieb:
> I wrote the spec. draft and implementation (in antlr) for Groovy 
> gstring syntax; I did the work with the intention of helping the JSR 
> 241 Groovy standard.  It could work in Java with adjustments, and the 
> Groovy spec. is detailed enough to be a starting point.   I don't 
> really have time to work on it though. That's why I haven't done a 
> proposal.
> 
> For Java, to extend the string syntax and emphasize that a new string 
> is being constructed, I recommend this:
> 
>    new "$foo, ${bar}s."
> 
> The new kwd enables the dollars. Other details to be taken from the 
> Groovy spec.
> 
> Best wishes,
> 
> -- John  (on my iPhone)
> 
> On Mar 19, 2009, at 8:33 AM, phil swenson <phil.swenson at gmail.com> 
> wrote:
> 
>  > funny, i just joined the list specifically to ask about this subject.
>  >
>  > why not just copy the groovy implementation of this?   $var or $
>  > {expresion} ?
>  > in groovy it would be:
>  > "[$field1, $field2, $field3]"
>  >
>  > or with the explicit expression syntax:
>  > "[${field1}, ${field2}, ${field3}]"
>  >
>  >
>  > I hate escape characters :)
>  >
>  >
>  > On Thu, Mar 19, 2009 at 2:03 AM, Schulz, Stefan <schulz at e-spirit.de> 
>  > wrote:
>  >> The concat-variant to me is even worse readable than the original +-
>  >> notation, having three consecutive commas in between.
>  >> The proposal already mentions concatenation of any kind as 
>  >> alternative, although not mentioning concat(). Maybe worth expanding.
>  >>
>  >> Stefan
>  >>
>  >>> -----Original Message-----
>  >>> From: rssh at gradsoft.com.ua [mailto:rssh at gradsoft.com.ua]
>  >>> Sent: Wednesday, March 18, 2009 8:58 PM
>  >>> To: Howard Lovatt
>  >>> Cc: coin-dev at openjdk.java.net; Schulz, Stefan
>  >>> Subject: Re: Proposal: Embedded Expressions for String Statements
>  >>>
>  >>>> I like Stefan's proposed syntax and as a way of a motivating 
>  >>>> example
>  >>>> consider writing a toString method that gives the field
>  >>> values within
>  >>>> square brackets, now you would write:
>  >>>>
>  >>>>     "[" + field1 + ", " + field2 + ", " + field3 + "]"
>  >>>>
>  >>>> With the proposal you would say:
>  >>>>
>  >>>>     "[\{field1}, \{field2}, \{field3}]"
>  >>>>
>  >>>> Which I find clearer.
>  >>>>
>  >>>
>  >>> Just note: now we can use much cleaner
>  >>>  concat( field1, ',' , field2, ',' field3 )
>  >>>
>  >>>
>  >>>
>  >>>> Many thanks to Stefan for writing this up formally.
>  >>>>
>  >>>>
>  >>>
>  >>>
>  >>>
>  >>>
>  >>
>  >>
>  >
>