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CGI Programming with Perl
Lesson 3: Operators
| Precedence | Operation | Arithmetic | String |
|---|
| 1 | AutoIncrement | ++ | |
| | AutoDecrement | -- | |
| 2 | negation | - | |
| 3 | Exponentiation | ** | |
| 4 | Multiplication | * | |
| | Division | / | |
| | Modulo | % | |
| | Repetition | | x |
| 5 | Addition | + | |
| | Subtraction | - | |
| | Concatenation | | . |
| 6 | less than | < | lt |
| | less than or equal to | <= | le |
| | greater than | > | gt |
| | greater than or equal to | >= | ge |
| 7 | equivalent | == | eq |
| | not equivalent | != | ne |
| | compare | <=> | cmp |
| 8 | NOT | ! | ! |
| 9 | AND | && | && |
| 10 | OR | || | || |
| 11 | Simple Assignment | = | = |
| | Multiplication and assignment | *= | |
| | Division and assignment | /= | |
| | Addition and assignment | += | |
| | Subtraction and assignment | -= | |
| | Remainder and assignment | %= | |
| | Exponentiation and assignment | **= | |
| | Bitwise AND and assignment | &= | |
| | Bitwise OR and assignment | |= | |
| | Bitwise XOR and assignment | ^= | |
| | String concatenation and assignment | | .= |
| | String repeat and assignment | | x= |
| 12 | mnemonic NOT | not | not |
| 13 | mnemonic AND | and | and |
| 14 | mnemonic OR | or | or |
Exercises
| 1 |
#! e:\perl\bin\perl.exe
# ask the user for a temperature and then ask
# whether to convert to Celsius or Fahrenheit.
print "Celsius / Fahrenheit Conversion\n";
print "Enter known temperature: ";
$temp = <STDIN>;
chomp $temp;
print "Convert to [C]elsius or [F]ahrenheit: ";
$convert = <STDIN>;
chomp $convert;
if ($convert eq "C" || $convert eq "c") {
print $temp . "F = " . (($temp - 32) * 5/9) . "C";
} elsif ($convert eq "F" || $convert eq "f") {
print $temp . "C = " . (($temp * 9/5) + 32) . "F";
} else {
print "Unknown Conversion Type " . $convert;
}
#!C:\perl\bin\perl.exe
# Exercise 3.1
# Temperature conversion
# Get the temperature from the user
print("Enter a positive integer: ");
$temp = <STDIN>;
chomp($temp);
# Get the conversion type from the user
print("Convert to degrees F or C (F/C)? ");
$type = <STDIN>;
chomp($type);
if ($type eq "F") {
$T = 9 * $temp / 5 + 32;
} else {
$T = 5 * ($temp - 32) / 9;
}
print("$T degrees $type\n");
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| 2 |
#!C:\perl\bin\perl.exe
# Exercise 3.2
# Sort two strings
# Get the first string
print("Enter first string: ");
$string1 = <STDIN>;
# Get the second string
print("Enter second string: ");
$string2 = <STDIN>;
# Test and print the strings in sorted order
# Note: newline character left
# on the end of the strings
print(($string1 ge $string2) ? $string2 : $string1);
print(($string1 lt $string2) ? $string2 : $string1);
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