SE3310 Final Flashcards
What is a set?
An unordered collection of unique elements
What is a language?
A set of strings
What is computation?
Finding answers to yes/no questions (such as, is s in L?)
What is the range of a function?
The set of all outputs
What is a Finite State Transducer?
A DFA with outputs defined (for each transition)
What is the domain of a function?
The set of all possible inputs
What is a regular language?
A language where there exists a finite automaton that recognized it
What are the 2 interpretations for how NFAs function?
- Parallel computation (execute all paths concurrently)
- Lucky guess (Always picks the correct path)
T/F: Every NFA has an equivalent DFA
T
T/F: Every DFA has an equivalent NFA?
T - a DFA is an NFA silly
T/F: Regular languages are closed under kleene star
T
T/F: Regular languages are closed under complement
T
What are the 6 steps in the pumping lemma for regular languages proof?
- Assume L is regular
- Let p = pumping length
- Pick string s (s must be in L, and size of s >= p)
- Examine all cases for dividing s = xyz
- For each case, find value i such that s’=x y^i z
- Conclude that there is no way to divide s into 3 parts xyz such that y can be pumped. Therefore L is not regular.
T/F: All context free languages are regular
F : regular languages are a subset of context free languages
T/F: All DFA’s have an equivalent CFG
T
What are the restrictions on the size of y in the pumping lemma for regular languages proof?
|y| > 0
|xy| <= p
What is a pushdown automaton?
Essentially an NFA with ability to read/write from a stack
What are the components of a turing machine?
- tape
- head
- control
What are the requirements for an algorithm / effective method?
- Finite # steps
- Always produces results
- Result is always correct
- Could in principle be done by human
- Only needs to follow instruction
What does the church-turing thesis declare?
Every effectively calculable function is a computable function (i.e. A problem can only be solved by an algorithm if it can be solved by a TM)
What is a recursive language?
A decidable language: M decides L if it halts and accepts all s in L AND halts and rejects for all s NOT in L
What is a recursively-enumerable languages?
A recognizable language: M recognizes L if it halts and accepts all s in L