<![CDATA[
Ruby Language Overview handout #9
Summary of Ruby features
numbers: Integer (3, 802), Float (3.4)
booleans: true, false
strings: "hello", "how are you?"
arrays: [3, 15, "hello", [7, "howdy"], 308.4, true]
ranges: 1..10, 'a'..'z'
hash: {"stuart"=>"reges", "donald"=>"trump"} Hash.new(default value)
enumerators: n.times, x.each
class Foo [< <superclass>]
<definitions>
end
def f(p1, p2, ..., pn)
<body>
end
def f(p1 = v1, p2 = v2, ..., pn = vn)
<body>
end
attr_reader symbol1, symbol2, ..., symbol-n
attr_writer symbol1, symbol2, ..., symbol-n
constructor is "initialize", self is implicit parameter, clone makes a copy
public/protected/private keywords used inside a class mean "starting here"
use prefix @ for instance variables, @@ for class variables, : for symbols
if <bool-expr> [then]
<body>
elsif <bool-expr> [then]
<body>
else
<body>
end
while <bool-expr> [do]
<body>
end
for <variable> in <collection> [do]
<body>
end
loop do
<statements>
break if <bool-expr>
<statements>
end
<variable>.<method>(<params>) { <block> }
<variable>.<method>(<params>) do
<block>
end
<block> can begin with |params| and has a sequence of statements
"text before #{expression to evaluate} text after"
a method takes a block if it includes calls on yield
nil is a special value that represents "no object"
Useful methods
arithmetic: +, -, *, /, %, ** (exponentiation), +=, -=, *=
mathematical: n.abs, Math.[sqrt, sin, cos, log, log10]
relational: <, >, <=, >=, !=, ==, <=>
logical: &&, ||, !, and, or, not
conversion: <Integer>.to_f, <Float>.[round, to_i], <Object>.to_s
random: rand, rand(<integer>)
higher-order: map, filter, find, find_all, any?, all?, inject, reduce
Array/String:
x.length # of elements (also Hash, size is a synonym)
x[i] element i (0-based indexing, also Hash)
x[i, n] slice with n elements starting at i
x[i..j] slice with values at index i through j
x << v append v to x
x.index v index of v in x
x.delete v delete all occurrences of v from x (also Hash)
x.reverse values in reverse order
x.sort sort values (Arrays only)
push v appends v to end of array (Arrays only)
pop remove and return top value (Arrays only)
chomp eliminate trailing newline from string (String only)
upcase/downcase uppercase/lowercase version of string (String only)
split, split("") split on whitespace, split characters (String only)
each_with_index yield value/index pairs (Arrays/Hash only)
x.member? v does it contain v? (Arrays/Hash only)
Input/Output
puts x like Java println
print x like Java print (stay on current output line)
print x, y print multiple values
gets reads a line of input
File.open(s) returns a file object for given file (implements each)
<file>.gets read a line from file object
]]>