plus
:: RE a -> RE a
We can extend the language of regular expressions by standard abstractions. |
sem
:: RE a -> [a]
The semantics of regular expressions can be defined as a nondeterministic operation associating any word of the language defined by the regular expression: |
match
:: RE a -> [a] -> Bool
An operation to match a string against a regular expression can be defined by the following constraint: |
grep
:: RE a -> [a] -> Bool
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grepShow
:: RE a -> [a] -> [a]
The following operation extends the operation grep to return
the substring which starts with the regular expression.
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grepPos
:: RE a -> [a] -> Int
The following operation extends the operation grep to return
the position where the matched regular expression starts.
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A data type to represent regular expression over some alphabet. A regular expression is either a literal, i.e., a member of the alphabet, an choice between two regular expressions, the concatenation of two regular expressions, or the repetition of a regular expression.
Constructors:
Lit
:: a -> RE a
Alt
:: (RE a) -> (RE a) -> RE a
Conc
:: (RE a) -> (RE a) -> RE a
Star
:: (RE a) -> RE a
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We can extend the language of regular expressions by standard abstractions. Here we introduce an operator denoting at least one or more repetitions of a regular expression:
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The semantics of regular expressions can be defined as a nondeterministic operation associating any word of the language defined by the regular expression:
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An operation to match a string against a regular expression can be defined by the following constraint:
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