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["Rosu, Grigore" <grosu AT illinois.edu>]

Thanks Dwight, but let's face it: we cannot prolong this for too long 
anymore, we need to provide full lexing support in the tool.  SDF already 
does it, so it is only a matter of wrapping it up.  Radu, we can use the 
syntax that we discussed a couple of months ago, something like this if I 
remember correctly:

  syntax MyID ::= Token("[A-Za-z$#][0-9A-Za-Z]*")

This should not be too hard to support, although I let Radu speak for that, 
because there are several parsers that need to be convinced to work.

Grigore



________________________________________
From: 
k-user-bounces AT cs.uiuc.edu
 
[k-user-bounces AT cs.uiuc.edu]
 on behalf of Guth, Dwight 
[dguth2 AT illinois.edu]
Sent: Friday, February 01, 2013 7:41 AM
To: Daniele Filaretti; 
k-user AT cs.uiuc.edu
Subject: Re: [K-user] resolving variable names inside double quoted strings 
(as in PHP)

I actually just implemented a very similar feature in my python semantics 
concerning str.format. As part of that I implemented some custom string 
processing functions that you may find useful. It allowed me to very cleanly 
iterate through the string, pause at each escape character, and write a rule 
that customizes the behavior for each one. You are welcome to take a look at 
it as soon as I push my commit upstream later today to 
http://code.google.com/p/k-python-semantics/source/browse/python-semantics-strings.k

If you like the solution you're free to use as much or as little of my code 
as you want. You're free to ask me any questions you have about the code too.

Daniele Filaretti 
<dfilaretti AT gmail.com>
 wrote:


Hi all,

In PHP (the language I'm trying to define in K) when a variable name occurs 
in a string (variable names always start with $) the value of that variable 
is found in the environment and printed into the string. For example:

> $x = "Daniele";
> echo "Hello $x!"
>
> out>> "Hello Daniele!"

Until now I ignored this in my definition - i.e., I'm using builtin strings 
that K offer, and I can achieve the same with (that is also legal in PHP):

> $x = "Daniele";
> echo "Hello " . $x . "!"
>
> out>> "Hello Daniele!"

However, I noticed that the feature is heavily used (of course, as it's a 
very handy shortcut), so I decided to add it.

I'm currently having a look at the C definition by Chucky Ellison, as I think 
something similar has to be done for C's 'printf". However, it seems that 
their solution is very low level (scanning a string character by character 
and defining some kind of state machine I guess), and perhaps I don't need 
that level of detail.

Ideally, all I need is just something like a string tokenizer.
For example if my string is

> "Hello $x!"

I would like to obtain a list (containing strings and variables) :

> ["Hello", $x, "!"]

with this list I could easily print the elements that are already strings, 
and evaluate the variable names before printing them as well (using my 
already defined printing function for strings -- sending to it the elements 
of my list one by one).

Any ideas? Comments? Suggestions?

Thanks a lot to everyone!

Cheers,
Daniele
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