Programming Ruby
The Pragmatic Programmer's Guide
class Range
Parent:
Object
Version:
1.6
Index:
new
===
begin
each
end
exclude_end?
first
last
length
size
A
Range represents an interval---a set of values with a start
and an end. Ranges may be constructed using the
s
..
e and
s
...
e literals, or
with
Range.new
. Ranges constructed using
.. run from the
start to the end inclusively. Those created using
... exclude the
end value. When used as an iterator, ranges return each value in
the sequence.
(-1..-5).to_a
サ
[]
(-5..-1).to_a
サ
[-5, -4, -3, -2, -1]
('a'..'e').to_a
サ
["a", "b", "c", "d", "e"]
('a'...'e').to_a
サ
["a", "b", "c", "d"]
Ranges can be constructed using objects of any type, as long as the
objects can be compared using their
<=> operator and they
support the
succ method to return the next object in
sequence.
class Xs # represent a string of 'x's
include Comparable
attr :length
def initialize(n)
@length = n
end
def succ
Xs.new(@length + 1)
end
def <=>(other)
raise TypeError unless other.kind_of? Xs
@length <=> other.length
end
def inspect
'x' * @length
end
end
r = Xs.new(3)..Xs.new(6)
サ
xxx..xxxxxx
r.to_a
サ
[xxx, xxxx, xxxxx, xxxxxx]
r.member?(Xs.new(5))
サ
true
mixins
Enumerable:
collect, detect, each_with_index, entries, find, find_all, grep,
include?, map, max, member?, min, reject, select, sort, to_a
class methods
new
Range.new(
start,
end,
exclusive
=false )
->
aRange
Constructs a range using the given
start and
end. If the
third parameter is omitted or is
false, the range will
include the end object; otherwise, it will be excluded.
instance methods
===
rng ===
anObject ->
true or
false
Returns
true if
anObject is an element of
rng,
false otherwise. Conveniently,
=== is the comparison
operator used by
case statements.
case 79
when 1..50 then print "low\n"
when 51..75 then print "medium\n"
when 76..100 then print "high\n"
end
produces:
begin
rng.begin ->
anObject
Returns the first object of
rng.
each
rng.each {| i | block }
->
rng
Iterates over the elements
rng, passing each in turn to the
block.
(10..15).each do |n|
print n, ' '
end
produces:
Returns the object that defines the end of
rng. See also
Range#length
.
(1..10).end
サ
10
(1...10).end
サ
10
Returns
true if
rng excludes its end value.
first
rng.first ->
anObject
Returns the first object in
rng.
last
rng.last ->
anObject
Synonym for
Range#end
.
length
rng.length ->
anInteger
Returns the number of objects in
rng.
(1..10).length
サ
10
(1...10).length
サ
9
size
rng.size ->
anInteger
Synonym for
Range#length
.
Extracted from the book "Programming Ruby -
The Pragmatic Programmer's Guide"
Copyright
©
2001 by Addison Wesley Longman, Inc. This material may
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Distribution of substantively modified versions of this document is
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