CST229 Week 3
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Questions or concern?
Homework #2 due
Hand back Homework #1
Reading: Chapters 4 & 5
Language Definitions Review
– Set notation
– Recursive Definition
• Chapter 4 – yet another language definition
• In-Class Exercise#3
• Chapter 5 – Machine to recognize languages (if
time)
In-Class Exercise #3
Write regular expressions for the following
languages over {a, b}:
1. All strings that have exactly one double letter
(aa or bb) in them.
2. All words that do not have the substring ab
3. All strings in which any b’s that occur are
found in clumps of an odd number at a time,
such as abaabbbab