• a Character matches this character.

 
•  a character class '[' (Character|Character'-'Character)+ ']' matches any character in that class. A Character is to be considered an element of a class, if it is listed in the class or if its code lies within a listed character range Character'-'Character. So [a0-3\n] for instance matches the characters

 

 

a 0 1 2 3 \n
 

•  a negated character class '[^' (Character|Character'-'Character)+ ']' matches all characters not listed in the class.

 
•  a string '"' StringCharacter+ '" ' matches the exact text enclosed in double quotes. All meta characters but \ and " loose their special meaning inside a string.

• a macro usage '{' Identifier '}' matches the input that is matched by the right hand side of the macro with name "Identifier".

 
•  a predefined character class matches any of the characters in that class. There are the following predefined character classes:

 

 

. contains all characters but \n.

a | b

 

 

(union) is the regular expression, that matches all input that is matched by a or by b.

a b

 

 

(concatenation) is the regular expression, that matches the input matched by a followed by the input matched by b.

a*

 

 

(kleene closure) matches zero or more repetitions of the input matched by a

a+

is equivalent to aa*

a?

matches the empty input or the input matched by a

a{ n}

 

 

is equivalent to n times the concatenation of a. So a{4} for instance is equivalent to the expression a a a a. The decimal integer n must be positive.

a{ n,m}

 

 

is equivalent to at least n times and at most m times the concatenation of a. So a{2,4} for instance is equivalent to the expression a a a? a?. Both n and m are non negative decimal integers and m must not be smaller than n.

( a )

matches the same input as a.

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