Prepends the given objects to self:
a = [:foo, 'bar', 2] a.unshift(:bam, :bat) # => [:bam, :bat, :foo, "bar", 2]
Array#prepend is an alias for Array#unshift.
Returns a count of specified elements.
With no argument and no block, returns the count of all elements:
[0, 1, 2].count # => 3 [].count # => 0
With argument obj, returns the count of elements == to obj:
[0, 1, 2, 0.0].count(0) # => 2 [0, 1, 2].count(3) # => 0
With no argument and a block given, calls the block with each element; returns the count of elements for which the block returns a truthy value:
[0, 1, 2, 3].count {|element| element > 1} # => 2
With argument obj and a block given, issues a warning, ignores the block, and returns the count of elements == to obj.
Returns self truncated (toward zero) to a precision of ndigits decimal digits.
When ndigits is negative, the returned value has at least ndigits.abs trailing zeros:
555.truncate(-1) # => 550 555.truncate(-2) # => 500 -555.truncate(-2) # => -500
Returns self when ndigits is zero or positive.
555.truncate # => 555 555.truncate(50) # => 555
Related: Integer#round.
Returns self rounded to the nearest value with a precision of ndigits decimal digits.
When ndigits is negative, the returned value has at least ndigits.abs trailing zeros:
555.round(-1) # => 560 555.round(-2) # => 600 555.round(-3) # => 1000 -555.round(-2) # => -600 555.round(-4) # => 0
Returns self when ndigits is zero or positive.
555.round # => 555 555.round(1) # => 555 555.round(50) # => 555
If keyword argument half is given, and self is equidistant from the two candidate values, the rounding is according to the given half value:
:up or nil: round away from zero:
25.round(-1, half: :up) # => 30 (-25).round(-1, half: :up) # => -30
:down: round toward zero:
25.round(-1, half: :down) # => 20 (-25).round(-1, half: :down) # => -20
:even: round toward the candidate whose last nonzero digit is even:
25.round(-1, half: :even) # => 20 15.round(-1, half: :even) # => 20 (-25).round(-1, half: :even) # => -20
Raises and exception if the value for half is invalid.
Related: Integer#truncate.
Returns the absolute part of its polar form.
Complex(-1).abs #=> 1 Complex(3.0, -4.0).abs #=> 5.0
Returns true if cmp‘s real and imaginary parts are both finite numbers, otherwise returns false.
Returns 1 if cmp‘s real or imaginary part is an infinite number, otherwise returns nil.
For example: (1+1i).infinite? #=> nil (Float::INFINITY + 1i).infinite? #=> 1
Only the object nil responds true to nil?.
Returns the absolute value of self.
12.abs #=> 12 (-34.56).abs #=> 34.56 -34.56.abs #=> 34.56
Numeric#magnitude is an alias for Numeric#abs.
Returns self rounded to the nearest value with a precision of digits decimal digits.
Numeric implements this by converting self to a Float and invoking Float#round.
Returns self truncated (toward zero) to a precision of digits decimal digits.
Numeric implements this by converting self to a Float and invoking Float#truncate.
Returns true if num is a finite number, otherwise returns false.
Returns nil, -1, or 1 depending on whether the value is finite, -Infinity, or +Infinity.
Extracts data from self, forming objects that become the elements of a new array; returns that array. See Packed Data.
Like String#unpack, but unpacks and returns only the first extracted object. See Packed Data.
Returns an unescaped version of self:
s_orig = "\f\x00\xff\\\"" # => "\f\u0000\xFF\\\"" s_dumped = s_orig.dump # => "\"\\f\\x00\\xFF\\\\\\\"\"" s_undumped = s_dumped.undump # => "\f\u0000\xFF\\\"" s_undumped == s_orig # => true
Related: String#dump (inverse of String#undump).
Returns the total number of characters in self that are specified by the given selectors (see Multiple Character Selectors):
a = "hello world" a.count "lo" #=> 5 a.count "lo", "o" #=> 2 a.count "hello", "^l" #=> 4 a.count "ej-m" #=> 4 "hello^world".count "\\^aeiou" #=> 4 "hello-world".count "a\\-eo" #=> 4 c = "hello world\\r\\n" c.count "\\" #=> 2 c.count "\\A" #=> 0 c.count "X-\\w" #=> 3
Returns self rounded to the nearest value with a precision of ndigits decimal digits.
When ndigits is non-negative, returns a float with ndigits after the decimal point (as available):
f = 12345.6789 f.round(1) # => 12345.7 f.round(3) # => 12345.679 f = -12345.6789 f.round(1) # => -12345.7 f.round(3) # => -12345.679
When ndigits is negative, returns an integer with at least ndigits.abs trailing zeros:
f = 12345.6789 f.round(0) # => 12346 f.round(-3) # => 12000 f = -12345.6789 f.round(0) # => -12346 f.round(-3) # => -12000
If keyword argument half is given, and self is equidistant from the two candidate values, the rounding is according to the given half value:
:up or nil: round away from zero:
2.5.round(half: :up) # => 3 3.5.round(half: :up) # => 4 (-2.5).round(half: :up) # => -3
:down: round toward zero:
2.5.round(half: :down) # => 2 3.5.round(half: :down) # => 3 (-2.5).round(half: :down) # => -2
:even: round toward the candidate whose last nonzero digit is even:
2.5.round(half: :even) # => 2 3.5.round(half: :even) # => 4 (-2.5).round(half: :even) # => -2
Raises and exception if the value for half is invalid.
Related: Float#truncate.
Returns self truncated (toward zero) to a precision of ndigits decimal digits.
When ndigits is positive, returns a float with ndigits digits after the decimal point (as available):
f = 12345.6789 f.truncate(1) # => 12345.6 f.truncate(3) # => 12345.678 f = -12345.6789 f.truncate(1) # => -12345.6 f.truncate(3) # => -12345.678
When ndigits is negative, returns an integer with at least ndigits.abs trailing zeros:
f = 12345.6789 f.truncate(0) # => 12345 f.truncate(-3) # => 12000 f = -12345.6789 f.truncate(0) # => -12345 f.truncate(-3) # => -12000
Note that the limited precision of floating-point arithmetic may lead to surprising results:
(0.3 / 0.1).truncate #=> 2 (!)
Related: Float#round.