1.10 Exercises
Exercise 1.1
What are the problems that might arise when dividing program code
into separate module files?
Exercise 1.2
What are the differences between libraries, modules, packages, and
namespaces?
Exercise 1.3
Write a module that finds modules on your computer.
Exercise 1.4
Where do the standard Perl distribution modules live on your computer?
Exercise 1.5
Research how Perl manages its namespaces.
Exercise 1.6
When might it be necessary to export names from a module? When might
it be useful? When might it be convenient? When might it be a very
bad idea?
Exercise 1.7
The program testGeneticcode contains the following
loop:
# Translate each three-base codon to an amino acid, and append to a protein
for(my $i=0; $i < (length($dna) - 2) ; $i += 3) {
$protein .= Geneticcode::codon2aa( substr($dna,$i,3) );
}
Here's another way to accomplish that loop:
# Translate each three-base codon to an amino acid, and append to a protein
my $i=0;
while (my $codon = substr($dna, $i += 3, 3) ) {
$protein .= Geneticcode::codon2aa( $codon );
}
Compare the two methods. Which is easier to understand? Which is
easier to maintain? Which is faster? Why?
Exercise 1.8
The subroutine codon2aa causes the entire program
to halt when it encounters a "bad"
codon in the data. Often (usually) it is best for a subroutine to
return some indication that it encountered a problem and let the
calling program decide how to handle it. It makes the subroutine more
generally useful if it isn't always halting the
program (although that is what you want to do sometimes).
Rewrite codon2aa and the calling program
testGeneticcode so that the subroutine returns
some errorperhaps the value undefand
the calling program checks for that error and performs some action.
Exercise 1.9
Write a separate module for each of the following: reading a file,
extracting FASTA sequence data, and printing sequence data to the
screen.
Exercise 1.10
Download, install, and use a module from CPAN.
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