Section 1
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Last updated
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Date created
Mar 1, 2020
Cards (81)
Section 1
(50 cards)
ord( )
Turns a character into its code point.
if control structure
if ($name gt 'fred') {
print "'$name' comes after 'fred' in sorted order.
";
}
Operator Precedence
2+3*4
single-quoted string literal
A sequence of characters enclosed in single quotes.
floating-point literals
Numbers with and without decimal points are allowed (including an optional plus or minus prefix), as well as tacking on a power-of-10 indicator with E notation
The "leading zero" indicator works only for __________
literals
Perl allows you to add __________ for clarity within integer literals.
underscores
A literal is __________
how you represent a value in your source code -- it's data that you type directly into your program.
left associativity
Proceed front to back. Use parentheses when you don't remember the order of operations.
Perl computes with _________ values
double-precision floating-point values
The oct( ) function
oct('0377') # 255 decimal (only works on strings)
-M
Load the pragma only when needed. $ perl -Mdiagnostics ./my_program
diagnostics pragma
Get a longer description of the problem. use diagnostics;
empty string
has no characters
All numbers have (the same / different) formats internally.
the same
Comparison Operators
< <= == >= > != Each of these returns a true or false value.
The advantage of warnings over -w
You only turn on warnings for the file in which you use the pragma, whereas -w turns on for the entire program.
-w
$ perl -w my_program (Turns on warnings from the command line or sh-,bang line.) line: #!/usr/bin/perl -w
Perl identifier
A letter or underscore, and then possibly more letters, or digits, or underscores.
strings
Sequences of characters, such as hello or ☃★๛
Hexadecimal literals start with a __________ and use _________
leading 0x and use the digits 0 to 9 and the letters A through F (or a through f) to represent the values from 0 to 15
say
use v5.10; say "The answer is ", 6 * 7, '.';
Octal (base 8) literals start with a __________ and use the digits from ___ to ___.
leading 0 and use the digits from 0 to 7
assignment
The way to give a value to a variable. Takes a variable name on the left side, and gives it the value of the expression on the right.
Variable
Name for a container that holds one or more values.
Binary (base 2) literals start with a leading _____ and use __________.
0b and use only the digits 0 and 1
else
if ($name gt 'fred') {
print "'$name' comes after 'fred' in sorted order.
";
} else {
print "'$name' does not come after 'fred'.
"; print "Maybe it's the same string, in fact.
";
}
pragma
Something that tells the Perl compiler how to act.
the utf8 pragma
use utf8; Enables you to use Unicode characters in your program.
operators
Perl's verbs -- They decide how to treat the nouns.
variable interpolation OR double-quote interpolation
meal = "brontosaurus steak"; $barney = "fred ate a $meal"; # $barney is now "fred ate a brontosaurus steak" Another way to write that: barney = 'fred ate a ' . $meal; #
compound assignment operator
$fred = $fred + 5; $fred += 5; $str = $str . " "; fred **= 3
exponentiatial operator
2**3, is two to the third power, or eight.
modulus operator (%)
The value of the expression 10 % 3 is the remainder when 10 is divided by 3, which is 1.
escape
'Don\'t let an apostrophe end this string prematurely!'
sigil
The $ that indicates a scalar variable
hexadecimal floating-point literals
Instead of an e to mark the exponent, you use a p for the power of 2 exponent. Just like the hexadecimal integers, these start with 0x: 0x1f.0p3
string comparison operators
lt, le, eq, ge, gt, and ne
code point
$alef = chr( 0x05D0 ); $alpha = chr( hex('03B1') ); $omega = chr( 0x03C9 );
An integer constant in the program is treated as
the equivalent floating-point value
scalar data
The values themselves.
scalar
A single thing -- the simplest kind of data that Perl manipulates.
right associativity
Proceed back to front. Use parentheses when you don't remember the order of operations.
print "The answer is "; print 6 * 7;
print ".
";
print "The answer is ", 6 * 7, ".
";
The hex( ) function
hex('DEADBEEF') # 3_735_928_559 decimal (only works on strings)
Octal, hexadecimal, decimal and binary numbers are __________ to Perl.
all the same
<STDIN>
standard input A line-input operator working on the filehandle STDIN
E notation
(also known as exponential notation).
scalar variables
Containers which can store a scalar value.
\x{}
hexadecimal representation "\x{03B1}\x{03C9}"
Section 2
(31 cards)