regex decimal validation

regex.txt

Reference: https://stackoverflow.com/questions/12117024/decimal-number-regular-expression-where-digit-after-decimal-is-optional
You need a regular expression like the following to do it properly:

/^[+-]?((\d+(\.\d*)?)|(\.\d+))$/
The same expression with whitespace, using the extended modifier (as supported by Perl):

/^  [+-]? ( (\d+ (\.\d*)?)  |  (\.\d+) ) $/x
or with comments:

/^           # Beginning of string
 [+-]?       # Optional plus or minus character
 (           # Followed by either:
   (           #   Start of first option
     \d+       #   One or more digits
     (\.\d*)?  #   Optionally followed by: one decimal point and zero or more digits
   )           #   End of first option
   |           # or
   (\.\d+)     #   One decimal point followed by one or more digits
 )           # End of grouping of the OR options
 $           # End of string (i.e. no extra characters remaining)
 /x          # Extended modifier (allows whitespace & comments in regular expression)
For example, it will match:

123
23.45
34.
.45
-123
-273.15
-42.
-.45
+516
+9.8
+2.
+.5
And will reject these non-numbers:

. (single decimal point)
-. (negative decimal point)
+. (plus decimal point)
(empty string)
The simpler solutions can incorrectly reject valid numbers or match these non-numbers.


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find non-breaking space \x{A0}
find brackets with any numbers \([0-9]+\)