PERL

2. PERL • Just like C but with its own set of quirks

3. Variables • There is no datatype • PERL is loosely typed language • Variables take on the data type of the data assigned to them • Two forms • Scalar: single-valued variable • Starts with a $ • Array: multi-valued (indexed) variable • Starts with a @

4. Scalar Variables • String type (surrounded by single quotes) $var = ‘CATG’; • Floating type $var = 47.235; • Integer type $var = 26;

5. Scalar String Operations • Search and replace $string = ‘ABC’; $string =~ s/B/b/g; • Note there is no space between the = and the ~ • =~ is the binding operator • Apply the operation on the right to the string on the left • Search and replace a set of characters $string =~ tr/AC/ac/; • Get the length of a string $len = length $string; • Testing for equality if ($string eq ‘ABC’) { # if covered later on

6. Array Variables • Initialized with a parenthesized list of values • Array of characters @arr = (‘A’, ‘B’, ‘C’); • Array of floating points @arr = (1.3, 2.2, 3.1); • Array of integers @arr = (3, 2, 1);

7. Array Variables • Print the entire array (no spaces between) print @arr, “\n”; • Print the entire array (spaces between) print “@arr”, “\n”; • Print (access) individual elements print $arr[0], “\n”; • Note the element is a scalar, $

8. Array Variables • Getting the length of an array $arrLength = scalar @arr; • Remove the last element of an array $last = pop @arr; • Remove the first element of an array $first = shift @arr; • Reverse an array @rev = reverse @arr;

9. Array Variables • Insert an element splice (@arr, 0, 0, 10); # beginning splice (@arr, 3, 0, 4); # index 3 • Add an element to the beginning unshift (@arr, 6); • Add an element to the end push (@arr, 7); • Combine elements into a single scalar string $allelements = join( ‘’, @arr); # first parameter # is the separater

10. Homework • Chapter 4, Exercises 4-1 thru 4-5 • Basically, practice all the stuff we did in class • Not to be collected