Question

Regular expression (x/y)(x/y) denotes which of the following set?

(a) {xy,xy}

(b) {xx,xy,yx,yy}

(c) {x,y}

(d) {x,y,xy}

I have been asked this question in my homework.

This intriguing question originated from Finite Automata and Regular Expressions in chapter Compiler Introduction of Compiler

Answer 1

Right option is (b) {xx,xy,yx,yy}

Easiest explanation: From first part if we take x then from the latter part x then it forms xx

From first part if we take x then from the latter part y then it forms xy

From first part if we take y then from the latter part x then it forms yx

From first part if we take y then from the latter part y then it forms yy.