MATLAB POLYSPACE 7 Guide d'installation télécharger pdf (Page 412)

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6 Editing and Debugging M-Files

thatareonthesearchpath.Ifallfilestobeusedareinthesamedirectory,

you can instead m ake that directory be the current directory.

Debugging Example — The Collatz Problem

The debugging process and features are best described via an example.

Topreparetousetheexample,createtwoM-files,

collatz.m and

collatzplot.m, that produce data for the Collatz problem.

For any given p os itiv e integer,

n,theCollatz function produces a sequence of

numbers that always resolves to 1. If

n is even, divide it by 2 to get the next

integer in the sequence. If

n is odd, multiply it by 3 and add 1 to get the next

integer in the se quence. Repeat the steps until the next integer is 1. The

number of integers in the sequence varies, depending on the starting value,

The Collatz problem is to prove that the Collatz function will resolve to 1 for

all p ositive integers. The M-files for this e xample are useful for studying

the Collatz problem. The file

collatz.m generates the sequence of integers

for any given

n.Thefilecollatzplot.m calculates the number of integers

in the sequence for all integers from 1 through

m,andplotstheresults. The

plot shows patterns that can be further studied.

Follow ing are the results when

n is 1, 2, or 3.

n Sequence

Number of Integers in the

Sequence

11 1

221 2

3 3105168421 8

M-Files for the Collatz Problem. Fo ll owing are the two M- fi les you use for

the debugging example. To create these files on your system, open two new

M-files. Select and copy the following code from the Help browser and paste

it into the M-files. Save and name the files

collatz.m and collatzplot.m.

Save them to your current directory or add the directory wh ere you save them

to the search path. One of the files has an embedded error to illustrate the

debugging features.

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MATLAB POLYSPACE 7 Guide d'installation Page 412

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