• BUILD: make
• EXAMPLE RUN: make run
• ARBITRARY RUN: ./flp20-log < /tests/04.in

A program implements the simulation of the non-deterministic Turing Machines.
The program reads the transitions and initial content of the machine tape
from the standard input. The transitions have to be in the required following
format: State, Symbol, NewState, NewSymbol, where State and NewState are
in the range [A-Z], Symbol and NewSymbol are within the range [a-z],
or they can be also space, which represents the blank symbol on the
machine tape. Moreover, the NewSymbol can be equal to L or R, which
represents the shift of the machine head to the left or right. The states
S and F represents the starting respectively the finish state of the
given machine. The initial content of the machine tape has to be symbols
within the range [a-z] and it has to be in the last line of the input.
The example inputs you can find in the test directory, respectively in
the *.in files.

In the beginning, the given input is loading and subsequently, it is stored
to the internal representation. We note, when some transition has not the
required format, then it will ignore during the simulation of the given
machine. The correctly loaded transitions are storing to the database before
the start of the simulation (transition). Into the database is also stored
the initial configuration, which consists of the initial state S and
given initial content of the machine tape (paths). In the first step, the
simulation finds all firing transitions from this configuration. Subsequently,
these transitions are fired and are constructed the new reachable
configurations. These newly constructed configurations are appended to the
stored paths in the database. After the first step will be in the database
stored only the paths with the length equal to two. When some newly
constructed configuration includes the final state F, then the computation
halts, otherwise, the next step is performed for these configurations.
Thus, in this way, after each step, we obtain all reachable configurations
after the relevant number of performed transitions, and in the database
will be stored the paths from the initial configuration to these reachable
configurations. In this iterative way, we will research all reachable
computation paths, and we are so guaranteed that if there is any path to
the final state F, the simulation will find it. At the end of the
computation, when was founded path to the final state, then it is written
out to the standard output.

The simulation of the computation of the Turing Machine can terminate in the
following different way. When exists the path from the initial configuration
to the configuration which including the final state, then it will be found
and write out to the standard output. When such the path does not exist
and the machine does not offer any other fireable transitions, then
the computation will halt with the message about the abnormally stopping.
To this option also belongs the not allowed the shift of the machine head
to the left outside the machine tape. The last possibility is that the
machine contains an infinite path where infinitely many transitions are
fired, in which case the simulation does not end spontaneously.

The test directory contains the shell script that serves
to automatic testing the correctness of this program. In total, the
test directory includes 13 different inputs, which are considered
to various aspects of the simulation such as possible infinite iterating
when the final path exists (test_10), potential delta symbols within
transitions (test_6) or inputs that do not include the finite
final paths (test_3), and much more. To run the shell script
you can use the following command:

make test

The output will be contained the resulting summaries from tested suites.
When some test is not successful, then is also printed the expected
solution in comparison to the solution generated by the program.

We list the run-times of the simulation at the individual testing
inputs from the attached directory:

• 01: 0.080s (2); 02: 0.071s (4); 03: 0.066s (e)
• 04: 0.083s (8); 05: 0.056s (5); 06: 0.066s (4)
• 07: 0.054s (5); 08: 0.086s (e); 09: 2.814s (35)
• 10: 0.069s (8); 11: 0.061s (4); 12: 0.065s (8)
• 13: 0.055s (e)