8.1 Ex – Parsing using a Finite State Machine (FSM) algorithm
A finite state machine also known as a finite state acceptor is a theoretical machine or algorithm
that uses a table to determine its current state and its action. The system is described with states.
Then depending on the current state and on the input you go to a new state and perform some
action. The operation of parsing is to convert a string into its meaningful data. For example to
convert a string into a real number. In this example we are going to convert a string into a real
number or double. We decompose the problem into 4 states:
State 0:
Represents the starting and ending state. It says we have not yet started and are still
expecting the first meaningful data in the number.
State 1:
In this state we have seen the sign of the value, if for example one put a ““ or “+”
sign in front of the number.
State 2:
In this state the algorithm is seeing the digits to the left of the decimal. It must
multiply the sum by 10 and add the value of the new digit.
State 3:
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 Spring '05
 Fernando
 Addition, Numerical digit, Decimal

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