RegEx - 不解析句子末尾的点（。）

Question

C# .Net4.5

I have the following regEx expression

^([0-9A-Z.]?[0-9a-z.]*\b\s*)+$

What this should do is match on a sentence where the words in the sentence may have a capital at the start of the word but not after the first letter and it may have a dot(.) anywhere within the sentence.

The expression words with the following

• This Works
• Th.is Wo.rks

But it doesn't work if the dot is at the end of a word

• Does not Work.
• This. Does not Work

Why doesn't this work if the dot(.) is at the end of a word?

Answer 1

Why doesn't this work if the dot(.) is at the end of a word?

\\b matches a word boundary, you don't have a period after that, so you don't get full stops at the end of words.

---

This seems closer:

^([0-9A-Z.]?[0-9a-z.]*(?:\b|\s)\.*)+$

I've added an or for word boundary and space \\b|\\s and put a period in there too.

It matches all 4 of your sample lines.

This seems cleaner:

^([0-9A-Z.]?[0-9a-z.]*\s*)+$

( Example )

Answer 2

You don't need word boundary \\b since the characters are restricted
to [A-Za-z.\\s]

Why not keep it simple and just enforce that [AZ] can only exist on a whitespace
boundary. (below, \\s is replaced with \\h for brevity)

^\\h*(?:(?<!\\S)[AZ]|[\\da-z.\\h]+)+$

Formatted and tested:

 ^                     # BOS
 \h*                   # Optional leading whitespace
 (?:                   # Cluster group start
      (?<! \S )             # Whitespace boundary before capital
      [A-Z]                 # Single capital letter
   |                      # or,
      [\da-z.\h]+           # Multiple digits, lower case letters, dots or whitespace
 )+                    # Cluster group end, do 1 to many times
 $                     # EOS

Answer 3

Thanks for the help. I believe I finally have the answer

^(\s*[0-9A-Z.]?[0-9a-z.]*\b\s*[.|\s]*)+$

The reason I need the \\b is because I need the pattern to not match on words that have capitals in the middle of the word. When the /b is removed the pattern will match on words with capitals in the middle of the word