A Brief Introduction to PerlSlide 2IntroductionScalar DataVariablesOperatorsAssignment OperatorArithmetic OperatorsString OperatorsNumeric Comparison OperatorsString Comparison OperatorsTwo Special Features of PerlIf-Else Control StructuresExample: If-Else Control StructureWhile Control StructureExample: While Control StructureStandard InputExampleListsArraysSlide 21Part IIntroductionScalar DataVariables OperatorsIf-Else Control StructuresWhile Control StructuresStandard InputLists and ArraysPerl 1 - Created by Larry Wall in 1987Stable Release: Perl 5.10.1Two basic scalar data types: Numbers and StringsNumbers-Integers and Floating-Point Numbers have the same format.Ex. $v=8222222#v contains value of 8Strings-Sequences of Characters.-Can either be enclosed in single or double quotes.Ex. $v=“a”222222#v contains value of “a”Undef –For Numbers or Strings, there is a special value called undef. This is initially assigned to all variables and acts as a zero for numbers and a null or empty string for strings.A scalar variable holds a single scalar valueNames of any scalar variable must begin with the “$” symbol followed by a Perl identifierEx. $tom, $cs265AssignmentArithmeticStringNumeric ComparisonString Comparison=Ex. $cs = 265+, -, *, /Ex. $c = a + b (Addition)$c = a – b (Subtraction)$c = a * b (Multiplication)$c = a / b (Division)., x. (dot) – String ConcatenationEx. $cl = class, $ro = room, $cl . $ro = classroomx – String MultiplierEx. $cl x 2 = classclass==, !=, <,>,<=,>=eq, ne, lt, gt, le, ge1. Interpolation of scalars into strings◦Any scalar variable inside a double quoted string is replaced by its value. ◦Ex. $example=“example”; print "$example"; prints example2. Automatic conversion between numbers and strings◦Arguments of an arithmetic operator are automatically recognized as numbers, and arguments of a string operator as strings. ◦Ex. $one = 1, $two = 2..◦print $one*$two; prints 2◦print $one x $two; prints 11◦print $one . $two prints 12Conditional Loopif(…){ … } else { … }$expected = “apple”; $given = “pear”;if($expected eq $given){ print “Apple”} else { print “Other Fruit”}Conditional Loopwhile (…) { … }$num = 1;while ($num != 1111) { $num . $num;}Input in Perl is very convenient<STDIN> Ex. Typical Line of Code for input$line=<STDIN> # read a full line from standard input and store it in variable $line$line=<STDIN>; if($line eq "\n"){ print "This was an empty line.\n"; } else { print "This line was not empty.\n"; }Lists are also user friendly in PerlList Literals (representations of lists) ◦Ex. (1,2,3,4) # a list consisting of numbers 1,2,.. 4◦Ex. (1..10) # the same list as the one above, now created by the range operator($a ..$b) - the range determined by current values of $a and $b List Assignment Examples:Arrays are variables storing lists.@num = (1..100) # creates an array “num” with a numbers 1 through 100◦print $num[0] # prints out 1◦print $num[$#num] # prints out the largest index of the
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