Theory of Computing Your first task as a scanner designer is to turn each token into a regular expression.

First, describe what you want to write as RE in English.

Then, give the RE for it.

e.g. {a^n b^m | n >= 0 m >= 1}

English: 0 or more a's followed by 1 or more b's

RE: a^* b^+

Alphabet is {a,b}. OK to use e or /\ for empty strings.

A) {a^2n b^2m+1 | n >= 0 ; m >= 0 }

Describe the language completely in English:

RE for it:

B) {w | w has at least one pair of consecutive a's } only as and bs allowed

Describe the language completely in English:

RE for it: