Computability and Complexity/Formal Languages/Chomsky Hierarchy/sample PDA inputs

= Sample PDA Inputs =

These examples are for use with the perl PDA emulator provided at the bottom of ../Context Free Languages/. That page also contains a description of what a PDA is and how it works.

The specification for a machine that accepts any string of the form $$\{a^{n}b^{n}|n \ge 0\}$$: :States: q1 q2 q3 q4 :Start State: q1 :Accept States: q4 :alphabet: a b :stack alphabet: $ a :rules: q1 e e q4 $ q1 e e q2 $ q2 b a q3 e q2 a e q2 a q3 b a q3 e q3 e $ q4 e

Some sample inputs: these accept: a a b b

(the empty string)

a a a a a b b b b b

these reject: a a a b b b b b

a a a b b

A machine that accepts any string that consists of at least one 'a' followed by at least as many 'b's: :States: q1 q2 q3 q4 :Start State: q1 :Accept States: q4 :alphabet: a b :stack alphabet: $ a :rules: q3 b e q3 e q3 b a q3 e q2 b a q3 e q2 a e q2 a q1 e e q2 $ q3 e $ q4 e

Some sample inputs: these accept: a b

a a a b b b b b b b

these reject:

(the empty string)

a a a b b

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