Matcher.replaceAll(Function<MatchResult, String> f) [was: Re: hg: lambda/lambda/jdk: Pattern.splitAsStream.]

[Paul Sandoz]

Hi Jürgen,

Three issues:

- we should probably include replaceFirst

- we need to use different method names since replaceAll(null) is now ambiguous

- need tests :-) (see jdk/tests/java/util/regex/RegExTest.java)

While these are nice to have i am not sure they carry their weight given the time constraints we have. If you can help us provide a more complete solution the better chance we have of getting this into JDK8.

Thanks,
Paul.

On Apr 19, 2013, at 12:59 AM, jk at blackdown.de wrote:

> Hi Paul,
> 
> Paul Sandoz <paul.sandoz at oracle.com> writes:
> 
>> Hi Jürgen,
>> 
>> That seems useful as a more general approach than Matcher.replaceAll(String ) e.g.
>> 
>>  Matcher.replaceAll(Function<MatchResult, String> f)
>> 
>> Ben, thoughts?
> 
> like this?
> 
> # HG changeset patch
> # User Jürgen Kreileder <jk at blackdown.de>
> # Date 1366322703 -7200
> # Node ID 59766f458701af5fbb23d195dd48a928505f3306
> # Parent  3ec06ef568a8ded0a7ecc7624df9d3a025dad6bc
> Matcher.replaceAll(Function<MatchResult, String> f)
> 
> diff --git a/src/share/classes/java/util/regex/Matcher.java b/src/share/classes/java/util/regex/Matcher.java
> --- a/src/share/classes/java/util/regex/Matcher.java
> +++ b/src/share/classes/java/util/regex/Matcher.java
> @@ -25,6 +25,7 @@
> 
> package java.util.regex;
> 
> +import java.util.function.Function;
> 
> /**
>  * An engine that performs match operations on a {@link java.lang.CharSequence
> @@ -916,6 +917,54 @@
>     }
> 
>     /**
> +     * Replaces every subsequence of the input sequence that matches the
> +     * pattern with the string returned by the given replacement function.
> +     *
> +     * <p> This method first resets this matcher.  It then scans the input
> +     * sequence looking for matches of the pattern.  Characters that are not
> +     * part of any match are appended directly to the result string; each match
> +     * is replaced in the result by the string returned by the replacement
> +     * function.  The replacement strings may contain references to captured
> +     * subsequences as in the {@link #appendReplacement appendReplacement}
> +     * method.
> +     *
> +     * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
> +     * the string returned by the replacement function may cause the results to
> +     * be different than if they were being treated as a literal strings. Dollar
> +     * signs may be treated as references to captured subsequences as described
> +     * above, and backslashes are used to escape literal characters in the
> +     * replacement string.
> +     *
> +     * <p> Given the regular expression <tt>(\\w)(\\w*)</tt>, the input
> +     * <tt>"paTTern maTcher"</tt>, and the replacement function
> +     * <tt>m -> m.group(1).toUpperCase() + m.group(2).toLowerCase()</tt>, an
> +     * invocation of this method on a matcher for that expression would yield
> +     * the string <tt>"Pattern Matcher"</tt>. </p>
> +     *
> +     * <p> Invoking this method changes this matcher's state.  If the matcher
> +     * is to be used in further matching operations then it should first be
> +     * reset.  </p>
> +     *
> +     * @param  f
> +     *         The function providing replacement strings
> +     * @return  The string constructed by replacing each matching subsequence
> +     *          by the replacement string provide by the given function,
> +     *          substituting captured subsequences as needed
> +     * @since 1.8
> +     */
> +    public String replaceAll(Function<MatchResult, String> f) {
> +        reset();
> +        if (find()) {
> +            StringBuffer sb = new StringBuffer();
> +            do {
> +                appendReplacement(sb, f.apply(this));
> +            } while (find());
> +            return appendTail(sb).toString();
> +        }
> +        return text.toString();
> +    }
> +
> +    /**
>      * Replaces the first subsequence of the input sequence that matches the
>      * pattern with the given replacement string.
>      *
> ==
> 
> 
>     Juergen
> 
> 
>> On Apr 8, 2013, at 6:59 PM, jk at blackdown.de wrote:
>> 
>>> Hi Paul,
>>> 
>>> it would be nice if Pattern/Matcher offered a terse way to loop over all
>>> matches in a string and replace them via a callback.
>>> 
>>> E.g. I'm currently using something like this:
>>> 
>>> private static final PatternAndReplacement PASS2 = new PatternAndReplacement(
>>>       Pattern.compile("  ( "
>>>                       + "   \\A \\p{Punct}*"         // start of title…
>>>                       + " |"
>>>                       + "   [:.;?!]\\ +"             // or of subsentence…
>>>                       + " | "
>>>                       + "   \\  ['\"“‘(\\[] \\ *"    // or of inserted subphrase…
>>>                       + ")"
>>>                       + "(" + SMALL_WORDS + ") \\b", // … followed by small word
>>>                       Pattern.COMMENTS | Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CHARACTER_CLASS),
>>>       m -> Matcher.quoteReplacement(m.group(1) + capitalize(m.group(2))));
>>> 
>>> with PatternAndReplacement being
>>> 
>>> private static class PatternReplacement implements Function<String, String> {
>>>   private final Pattern pattern;
>>>   private final Function<MatchResult, String> function;
>>> 
>>>   PatternReplacement(final Pattern p, final Function<MatchResult, String> f) {
>>>       pattern = p;
>>>       function = f;
>>>   }
>>> 
>>>   @Override
>>>   public final String apply(final String s) {
>>>       Matcher m = pattern.matcher(s);
>>>       if (m.find()) {
>>>           StringBuffer sb = new StringBuffer(s.length());
>>>           do {
>>>               m.appendReplacement(sb, function.apply(m));
>>>           } while (m.find());
>>>           return m.appendTail(sb).toString();
>>>       }
>>>       return s;
>>>   }
>>> }
>>> 
>>> Any plans for something like this?
>>> 
>>> 
>>> Jürgen
>>> 
>>> 
>>> paul.sandoz at oracle.com writes:
>>> 
>>>> Changeset: 526131346981
>>>> Author:    psandoz
>>>> Date:      2013-04-08 17:16 +0200
>>>> URL:       http://hg.openjdk.java.net/lambda/lambda/jdk/rev/526131346981
>>>> 
>>>> Pattern.splitAsStream.
>>>> Contributed-by: Ben Evans <benjamin.john.evans at gmail.com>
>>>> 
>>>> ! src/share/classes/java/util/regex/Pattern.java
>>>> + test-ng/tests/org/openjdk/tests/java/util/regex/PatternTest.java
>> 
> 
> -- 
> https://blackdown.de/