One might not hand-craft a regexp with single-entry character classes, but how about code-built regexps? When a regexp is built programatically, and there's a situation where one time a character class may contain one entry, and another times "n" entries, the fact that one-entry character classes are legal is simply one less thing to worry about. In that regard, I can see why it may be useful for such a construct to exist and to be legal.

And actually, there may be some single-entry character classes that are helpful, particularly among negated classes:

/[^T]ap/ # Match anything that's not 'T', followed by 'ap'

[download]

This is one time where a single-entry character class is actually probably the best way to do it.


Dave

In reply to Re: Why would one want in a regex a class with only a single entry? by davido
in thread Why would one want in a regex a class with only a single entry? by ack

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.