Re: [boost] Re: Re: Regex group substitution in 1.3

From: Thaddeus L. Olczyk (olczyk_at_[hidden])
Date: 2003-05-06 07:53:36

On Mon, 05 May 2003 22:18:57 -0400, Edward Diener
<eddielee_at_[hidden]> wrote:

>Thaddeus L. Olczyk wrote:
>> On Mon, 05 May 2003 18:47:15 -0400, Edward Diener
>> <eddielee_at_[hidden]> wrote:
>>
>>> Use regex_grep to find matches and then regex_format in the Predicate
>>> function to change each match to another value.
>>>
>> Excuse me, but I see no place in the documentation where it describes
>> a format string which says something like " take all of the string
>> sans subexpression and set the subexpressions to xxxx".
>>
>> Without that type of format string I do not see any way that
>> regex_format can do that.
>
>OK, I see now what you are trying to do. What about running a second
>regex_grep, after finding your initial match for the entire string in which
>you are searching, in which your regex string is:
>
>"\\$NAME|\\$ADDRESS|\\$EMAIL"
>
>Then when a match is found in your regex_grep, use regex_format to change to
>the appropriate substitution by testing, in the regex_grep predicate
>function, for which one of the matches has been found.
>
>>
>>> Thaddeus L. Olczyk wrote:
>>>> I've been searching the documentation for way to do regular
>>>> expression substitition of groups.
>>>>
>>>> For example: Given the regex;
>>>> "My[ ]+name[ ]+is[ ]+($NAME)[.]+
>>>> I[ ]+live[ ]+at[ ]+($ADDRESS)[.]+
>>>> My[ ]+email[ ]+address[ ]+is[ ]+($EMAIL)"
>>>>
>>>> I search some string for a match, find this:
>>>> "My   name is  $NAME . I live   at    $ADDRESS.
>>>> I am an acountant.  My email address is $EMAIL"
>>>>
>>>> and want to substitute
>>>> "Bob Smith" for $NAME
>>>> "1600 Pensylvania Ave." for $ADDRESS
>>>> "bob_at_[hidden]" for $EMAIL.

No. That won't work. You need to pin down
Unfortunately it is hard to find a realistic conterexample
for this simple example, but try.
"My   name is  $NAME . My  wife's name is  $NAME . 
  I live   at    $ADDRESS.  She lives   at    $ADDRESS.
  My email address is $EMAIL. Her email address is $EMAIL. "

With the regex
"name[ ]+is[ ]+($NAME)[.]+[ ]+live[s]?[ ]+at[ ]+($ADDRESS)[.]+
  [ ]+email[ ]+address[ ]+is[ ]+($EMAIL)"
Since it will result multiple substitutions for $NAME.

That being said, I posted the example because the language of regex's
can at times be ambiguous. It's better to answer the original question
rather than focus on the example. 

Thaddeus L. Olczyk
-----------------------
Think twice, code once.