String manipulation in Javalette By Daniel Bostrm and Sebastian - - PowerPoint PPT Presentation

String manipulation in Javalette

By Daniel Boström and Sebastian Salman http://www.dtek.chalmers.se/~salman/javalette/

Adding String Manipulation to Javalette

• Original version of Javalette lacked string

handling.

• Only support for strings was using the hardcoded

printString(“...”) function.

• No support for comparing strings or manipulating

them.

New String features

• Variables of type String can now be declared.
• Functions can accept parameters of the type

String.

• Strings can be compared to each other (!= == <

<= > >=).

• Strings can be compared to integers (will

compare with the length of the string).

• Possible to look for a matching sub string with

the / operator: boolean b = (“x” / “xyz”);

• Strings can be added like: String s =

“aoeu”+”htns”;

More features

Regular Expressions

• How to interpret and check the regex?
• Using Non-deterministic Finite Automata.
• Run the NFA with the string as input.

The NFA

• Three basic building blocks

– Concatenation

• ab

– Alternation

• a|b

– Star (Kleen closure)

• a*
• Using these, other rules can be formed

– a+ => aa*

Examples

int main() { printBool( regex_matches(“aab”, “aab”) ); //true printBool( regex_matches(“a*b”, “b”) ); //true printBool( regex_matches(“a+b”, “b”) ); //false return 0; }