Regular Expression
المؤلف:
Aho, A. V. and Ullman J. D
المصدر:
Theory of Parsing, Translation and Compiling, Vol. 1. Englewood Cliffs, NJ: Prentice Hall, 1972.
الجزء والصفحة:
...
8-2-2022
1301
Regular Expression
Regular expressions define formal languages as sets of strings over a finite alphabet. Let 
denote a selected alphabet. Then 
is a regular expression that denotes the empty set and 
is a regular expression that denotes the set containing the empty string as its only element.
If 
, then 
is a regular expression that denotes the set whose only element is string 
. If 
and 
are regular expressions denoting sets 
and 
, then
1. 
is a regular expression denoting the set 
, where 
denotes the union.
2. 
is a regular expression denoting the set of all concatenations of 
and 
, where 
and 
.
3. 
is a regular expression denoting closure of 
, that is, the set of zero or more concatenations of strings from 
The sets defined by regular expressions are called regular sets, and a set is regular iff it is defined by a right linear grammar.
REFERENCES
Aho, A. V. and Ullman J. D. Theory of Parsing, Translation and Compiling, Vol. 1. Englewood Cliffs, NJ: Prentice Hall, 1972.
Aho, A. V. and Ullman J. D. Theory of Parsing, Translation and Compiling, Vol. 2. Englewood Cliffs, NJ: Prentice Hall, 1972.
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