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Published on 2010-03-25T09:09:54Z
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Why is it counter intuitive?
/(?<!\d)\d{8}(?!\d)/,here (?<!\d) comes first,but called lookbehind,(?!\d) next,but called lookahead.All are counter intuitive.
What's the reason to name it this way?
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I have a list of variables:
variables = ['VariableA', 'VariableB','VariableC']
which I'm going to search for, line by line
ifile = open("temp.txt",'r')
d = {}
match = zeros(len(variables))
for line in ifile:
emptyCells=0
for i in range(len(variables)):
regex = r'('+variables[i]+r')[:|=|\(](-…
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I was looking at the regular expression for validating various data types from the (OWASP Regex Repository).
One of the regular expressions in there is called safetext and looks like:
^[a-zA-Z0-9\s.\-]+$
My first question is:
Is this regular expression correct?
complementary question
If this…
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I am writing a tool to help students learn regular expressions. I will probably be writing it in Java.
The idea is this: the student types in a regular expression and the tool shows which parts of a text will get matched by the regex. Simple enough.
But I want to support several different regex…
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I'm writing a piece of client-side javascript code that takes a function and finds the derivative of it, however, the regex that's supposed to match with the power rule fails to work in the context of the javascript program, even though it sucessfully matches when it's used with an independent regex…
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I need to be able to check for a pattern with | in them. For example an expression like d*|*t should return true for a string like "dtest|test".
I'm no regex hero so I just tried a couple of things, like:
Regex Pattern = new Regex("s*\|*d"); //unable to build because of single backslash
Regex Pattern…
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Hello, I am a bit puzzled with my Regex results (and still trying to get my head around the syntax). I have been using http://regexpal.com/ to test out my expression, and its works as intended there, however in C# its not as expected.
Here is a test - an expression of the following: (?=<open>)…
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Why is it counter intuitive?
/(?<!\d)\d{8}(?!\d)/,here (?<!\d) comes first,but called lookbehind,(?!\d) next,but called lookahead.All are counter intuitive.
What's the reason to name it this way?
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Hello again Stackoverflow people!
Assume I have these words: smartphones, smartphone
I want to match the substring "phone" from within them. However, in both case, I want only "phone" to be returned, not "phones" in the first case. In addition to this, I want matches only if the word "phone" is…
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How do I use lookahead assertion to determine if a certain character exist at most a certain number of times in a string.
For example, let's say I want to check a string that has at least one character to make sure that it contains "@" at most 2 times. Thanks in advance. Using python if that matters…
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I am reading an explanation (awesome "Parsing Techniques" by D.Grune and C.J.H.Jacobs; p.292 in the 2nd edition) about how to construct an LR(1) parser, and I am at the stage of building the initial NFA. What I don't understand is how to get/compute a lookahead symbol.
Here is the example from the…
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