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| + | Lexical analysis, the first step in the compilation process, splits the input data into segments and classifies them. Each segment of the input (a lexeme) will be assigned a label (the token). | ||
| + | |||
| + | In this case, we will be using regular expressions for recognizing portions of the input text. | ||
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== Regular Expressions == | == Regular Expressions == | ||
| + | Regular expressions are defined considering an alphabet { a, b, ..., c } and the empty string ''eps''. | ||
| + | * eps | ||
| + | * a | ||
| + | |||
| + | Primitive constructors: | ||
| + | * concatenation | ||
| + | * alternative | ||
| + | * Kleene-star (*) | ||
| + | |||
| + | Extensions: | ||
| + | * Transitive closure (+) - a+ ("one or more 'a'") | ||
| + | * Optionality (?) - a? ("zero or one 'a'") | ||
| + | * Character classes - [a-z] ("all chars in the 'a-z' range" - only one character is matched) | ||
== Recognizing Regular Expressions == | == Recognizing Regular Expressions == | ||
Lexical analysis, the first step in the compilation process, splits the input data into segments and classifies them. Each segment of the input (a lexeme) will be assigned a label (the token).
In this case, we will be using regular expressions for recognizing portions of the input text.
Regular expressions are defined considering an alphabet { a, b, ..., c } and the empty string eps.
Primitive constructors:
Extensions: