That means you really have to duplicate all of the RegEx into the negative lookahead to manually create the anchor you're after. The problem appears to be that while lookahead has an implicit anchor as to where it begins its match, there's no way of terminating where lookahead ends its search with an anchor based upon the result of another part of the RegEx. If "My" is at the end of the entire string, you'll never match anything because every lookahead will fail because they will all see that.
The first three words fail to match because My happens after them. The reason why lookahead doesn't work is because it fails in this relatively simple case: So after looking through these topics on RegEx's: lookahead, lookbehind, nesting, AND operator, recursion, subroutines, conditionals, anchors, and groups, I've come to the conclusion that there is no solution that satisfies what you're asking for. I'm STILL just wondering if there is a native regex construct that could do this. Where !Regex.IsMatch(m.Value, negativePattern) Return (from Match m in Regex.Matches(input, positivePattern) If there answer is "it does not exist and here is why." I'd like to know that too.Įdit 2: If I wanted to define my own function to do this it would be something like (here's a C# LINQ version): public static Match RegexMNI(string input, So.what about excluding matches that contain "My" somewhere in the middle?.I'm still really looking for a general construct, like a regex equivalent of the following pseudo-sql select from (Bohemian I still gave you an upvote for illustrating this). Like match ((?<=(so|me|^))big(com?plern) except when it starts with "My".Įdit: I realize that was a bad example, since excluding stuff at the begginning or end is a situation where negative look-ahead and look-behind expressions work. But i'm looking for a more general construct so that at least the large positive set can be a more complex expression. For this little example, sure, I could manually reconstruct something like, which is a pain but doable. I can't just say because that doesn't take into account the larger limiting set of only word characters. Note I'm subtracting a small set (the letter 'p') from a larger set (all word characters). This is hard to explain both completely and e Material Nonimplication for a formal definition.įor example, match any word character ( \w) EXCEPT 'p'. Find all strings from regular expression.I'm looking for a general regex construct to match everything in pattern x EXCEPT matches to pattern y.Extract all strings from regular expression.Generate all strings from regular expression.create all strings from regular expression.Describe the strings of the regular expression.This page contains the practice questions of regular expressions with solutions. A Regular Expression Strings that does not contain substring 110.Ī detailed tutorial of the regular expression is here in the link of regular expression tutorial.
A regular expression of the second last symbol is 1.RE for ending with b and having zero or multiple sets of aa and bb.Regular Expression (RE) for starting with 0 and ending with 1.Regular Expression for having strings of multiple double 1’s or null.Regular Expression for an odd number of 0’s or an odd number of 1’s in the strings.Regular Expression of starting with 0 and having multiple even 1’s or no 1.Regular Expression for strings having at least one double 0 or double 1.What is the regular expression (RE) for the language of all those strings starting with aa and ending with ba? Defined over ∑=