1. Strings and Languages
cs466(Prasad)
L2Lang

2. Alphabet String over (Finite) set of atomic elements / letters
Finite sequence of elements / letters from
Basis:
Inductive step:
Closure: …
cs466(Prasad)
L2Lang

3. Language over is a subset of . Examples
cs466(Prasad)
L2Lang

4. String Concatenation Recursive Definition (cf. defn. of +)
Signature: string string string
Recursive Definition (cf. defn. of +)
concatenation
primitive operation
cs466(Prasad)
L2Lang

5. String concatenation is associative. Implication
Order of performing concatenation is immaterial.
Parenthesis is redundant.
Other Examples
“+” and “*” on integers and matrices is associative, while “-” on integers is not.
Is NAND and NOR on booleans associative?
cs466(Prasad)
L2Lang

6. Refer to the text for the proof of associativity of the concatenation operation.
Refer to the text for the definition of reverse of a string and its properties.
cs466(Prasad)
L2Lang