RegExpr Help › Subexpressions
It's often useful to remember patterns that have been matched so that they can be used again. Subexpressions are used for this purpose.
Subexpressions look like this: (expression)
Anything matched inside the parentheses gets remembered and can be fetched with a call to RegExprResult.
Subexpressions are a useful way to extract and save several parts of the input at a time.
Example: Assume the following input: "Let a = x - 1". Regular expression "Let (\w+) = (.+)" will match the input. It has two subexpressions. Subexpression 1 will be "a" and subexpressions 2 will be "x - 1".
You can now retrieve the subexpressions by calling RegExprResult(1) and RegExprResult(2).
You can also match a subexpression in the same regular expression. This is useful for finding duplicated strings. Use the \digit syntax to match the digith subexpression. This is called backreferencing.
Example: Expression (\w+) \1 matches any word followed by a space and the same word again.
Backreferences work only after the subexpression has first been matched. That means a backreference must be located somewhere after the corresponding (expression).
Subexpressions can also be used for string substitution. For the details see RegExprSubst.
A total of 31 subexpressions can be specified. However, only 9 backreferences are available (\1 ... \9).
If you don't want to save a particular match, you can use the (?:expression) syntax. This is similar to (expression), but the match is not saved.
Regular expression syntax rules
VB functions in RegExpr
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