Common Regular Expression 2

8/19/2019 Common Regular Expression 2

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Prepared by: Genevieve C. Oca

AUTOMATA

(Regular Expression


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Co!!on

Opera"ors #orRegularOpera"ors


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Basic operators

$% &' escape . Arbi"rarycarac"er

)* carac"er class+ Op"ional

carac"er,% - repea"ed

expression al"erna"ive

/ beginning o# line 0 end o# line

1 "railing con"ex" 23 repe"i"ions


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Converts operators to text.

Exa!ples:

$+ rule #or a 4ues"ion !ar5

$, rule #or an as"eris5

&,' sa!e as above

a$-$- sa!e as &a--'

\, “” escape


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Stands for any character.

Exa!ples:

. Tis 6ill accep" one carac"er.oca. Tis 6ill accep" one carac"er

#ollo6ed by oca and ano"er carac"er

again. Exa!ple: vocal% local% e"c.

. Arbitrary character


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Basic operators








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A se" o# carac"ers "a" can !a"ca single inpu" carac"er.All opera"ors beco!e "ex" inside acarac"er class excep" "e#ollo6ing: 7 (das indica"es range / (care" indica"es co!ple!en" $ (bac5slas escapes 6i"incarac"er class

[ ] character class


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Basic operators








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9ero or one occurrence o# "epreceding expression.

)7-*+ op"ional nega"ive or posi"ivesignColou+r can !a"c color or colour

? ptional character


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Basic operators








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, : 8ero or !ore occurrences o#"e preceding expression.- : one or !ore occurrences o#"e preceding expression.

)a78A79=*)a78A797;=*,

7rule #or an iden"i>er)7-*+)7;*-

7rule #or a (signed in"eger

!, " repeated expression


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Any o# "e al"erna"ive expressions6ill be recogni8ed.

Exa!ple:?@BDF; a digi"% "e

ard 6ayocacu!eo6 can !a"c oca orcu or !eo6

# altrnative


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Te expression #ollo6ing "isopera"or 6ill only be !a"ced i##ound a#"er a ne6line carac"eror a" "e beginning o# "e inpu"s"rea!.

Exa!ple:/(abcd ab or cd 6ill berecogni8ed only i# a#"er $n

$ be%innin% of line


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Te #or!a" is: Expr?1Expr@. Tis!eans "a" Expr1 6ill berecogni8ed only i# #ound be#oreExpr2. Expr2 6ill no" beconsu!ed.

' trailin% context


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Basic operators








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Allo6s dieren" 5inds o# repe"i"ion.Exa!ple:a2?%3 "e sa!e as (a|aa|aaa|aaaa|

aaaa)a2?%3 "e sa!e as a+% one or !orerepe"i"ions o# a

a2@%3 "6o (@ or !ore repe"i"ions o# aa23 exac"ly >ve ( repe"i"ions o# a

()


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Basic operators








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$$,“* can do all thin%s thro+%h

Christho stren%thens -e”

/hilippians 0123

Common Regular Expression 2

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