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Class: Rational

Relationships & Source Files
Namespace Children
Classes:
compatible
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::Numeric
Instance Chain:
self, ::Numeric, ::Comparable
Inherits: Numeric
Defined in: rational.c

Overview

A rational number can be represented as a paired integer number; a/b (b>0). Where a is numerator and b is denominator. ::Integer a equals rational a/1 mathematically.

In ruby, you can create rational object with Rational, to_r, rationalize method or suffixing r to a literal. The return values will be irreducible.

Rational(1)      #=> (1/1)
Rational(2, 3)   #=> (2/3)
Rational(4, -6)  #=> (-2/3)
3.to_r           #=> (3/1)
2/3r             #=> (2/3)

You can also create rational object from floating-point numbers or strings.

Rational(0.3)    #=> (5404319552844595/18014398509481984)
Rational('0.3')  #=> (3/10)
Rational('2/3')  #=> (2/3)

0.3.to_r         #=> (5404319552844595/18014398509481984)
'0.3'.to_r       #=> (3/10)
'2/3'.to_r       #=> (2/3)
0.3.rationalize  #=> (3/10)

A rational object is an exact number, which helps you to write program without any rounding errors.

10.times.inject(0){|t,| t + 0.1}              #=> 0.9999999999999999
10.times.inject(0){|t,| t + Rational('0.1')}  #=> (1/1)

However, when an expression has inexact factor (numerical value or operation), will produce an inexact result.

Rational(10) / 3   #=> (10/3)
Rational(10) / 3.0 #=> 3.3333333333333335

Rational(-8) ** Rational(1, 3)
                   #=> (1.0000000000000002+1.7320508075688772i)

Instance Attribute Summary

::Numeric - Inherited

#finite?

Return true if num is finite number, oterwise returns false.
#infinite?

Returns values corresponding to the value of num's magnitude:
#integer?

Returns true if num is an ::Integer.
#negative?

Returns true if num is less than 0.
#nonzero?

Returns self if num is not zero, nil otherwise.
#positive?

Returns true if num is greater than 0.
#real

Returns self.
#real?

Returns true if num is a Real number.
#zero?

Returns true if num has a zero value.

Instance Method Summary

::Numeric - Inherited

#%

x.modulo(y) means x-y*(x/y).floor.
#+@

Unary Plus—Returns the receiver's value.
#-@

Unary Minus—Returns the receiver's value, negated.
#<=>

Returns zero if number equals other, otherwise nil is returned if the two values are incomparable.
#abs

Returns the absolute value of num.
#abs2

Returns square of self.
#angle

Alias for Numeric#arg.
#arg

Returns 0 if the value is positive, pi otherwise.
#ceil

Returns the smallest possible ::Integer that is greater than or equal to num.
#coerce,
#conj

Returns self.
#conjugate

Alias for Numeric#conj.
#denominator

Returns the denominator (always positive).
#div

Uses #/ to perform division, then converts the result to an integer.
#divmod

Returns an array containing the quotient and modulus obtained by dividing num by numeric.
#eql?

Returns true if num and numeric are the same type and have equal values.
#fdiv

Returns float division.
#floor

Returns the largest integer less than or equal to num.
#i

Returns the corresponding imaginary number.
#imag

Returns zero.
#imaginary

Alias for Numeric#imag.
#initialize_copy

Numerics are immutable values, which should not be copied.
#magnitude

Alias for Numeric#abs.
#modulo

Alias for Numeric#%.
#numerator

Returns the numerator.
#phase

Alias for Numeric#arg.
#polar

Returns an array; [num.abs, num.arg].
#quo

Returns most exact division (rational for integers, float for floats).
#rect

Returns an array; [num, 0].
#rectangular

Alias for Numeric#rect.
#remainder

x.remainder(y) means x-y*(x/y).truncate.
#round

Rounds num to a given precision in decimal digits (default 0 digits).
#singleton_method_added

Trap attempts to add methods to ::Numeric objects.
#step

Invokes the given block with the sequence of numbers starting at num, incremented by step (defaulted to 1) on each call.
#to_c

Returns the value as a complex.
#to_int

Invokes the child class's #to_i method to convert num to an integer.
#truncate

Returns num truncated to an ::Integer.

::Comparable - Included

#<

Compares two objects based on the receiver's #<=> method, returning true if it returns -1.
#<=

Compares two objects based on the receiver's #<=> method, returning true if it returns -1 or 0.
#==

Compares two objects based on the receiver's #<=> method, returning true if it returns 0.
#>

Compares two objects based on the receiver's #<=> method, returning true if it returns 1.
#>=

Compares two objects based on the receiver's #<=> method, returning true if it returns 0 or 1.
#between?

Returns false if obj #<=> min is less than zero or if anObject #<=> max is greater than zero, true otherwise.
#clamp

Returns min if obj #<=> min is less than zero, max if obj #<=> max is greater than zero and obj otherwise.

Instance Attribute Details

#exact? (readonly) Also known as: #rational?

#negative? ⇒ Boolean (readonly)

Returns true if rat is less than 0.

#positive? ⇒ Boolean (readonly)

Returns true if rat is greater than 0.

Instance Method Details

#*(numeric) ⇒ Numeric

Performs multiplication.

Rational(2, 3)  * Rational(2, 3)   #=> (4/9)
Rational(900)   * Rational(1)      #=> (900/1)
Rational(-2, 9) * Rational(-9, 2)  #=> (1/1)
Rational(9, 8)  * 4                #=> (9/2)
Rational(20, 9) * 9.8              #=> 21.77777777777778

#**(numeric) ⇒ Numeric

Performs exponentiation.

Rational(2)    ** Rational(3)    #=> (8/1)
Rational(10)   ** -2             #=> (1/100)
Rational(10)   ** -2.0           #=> 0.01
Rational(-4)   ** Rational(1,2)  #=> (1.2246063538223773e-16+2.0i)
Rational(1, 2) ** 0              #=> (1/1)
Rational(1, 2) ** 0.0            #=> 1.0

#+(numeric) ⇒ Numeric

Performs addition.

Rational(2, 3)  + Rational(2, 3)   #=> (4/3)
Rational(900)   + Rational(1)      #=> (901/1)
Rational(-2, 9) + Rational(-9, 2)  #=> (-85/18)
Rational(9, 8)  + 4                #=> (41/8)
Rational(20, 9) + 9.8              #=> 12.022222222222222

#-(numeric) ⇒ Numeric

Performs subtraction.

Rational(2, 3)  - Rational(2, 3)   #=> (0/1)
Rational(900)   - Rational(1)      #=> (899/1)
Rational(-2, 9) - Rational(-9, 2)  #=> (77/18)
Rational(9, 8)  - 4                #=> (23/8)
Rational(20, 9) - 9.8              #=> -7.577777777777778

#- ⇒ Rational

Negates rat.

#/(numeric) ⇒ Numeric #quo(numeric) ⇒ Numeric
Also known as: #quo

Performs division.

Rational(2, 3)  / Rational(2, 3)   #=> (1/1)
Rational(900)   / Rational(1)      #=> (900/1)
Rational(-2, 9) / Rational(-9, 2)  #=> (4/81)
Rational(9, 8)  / 4                #=> (9/32)
Rational(20, 9) / 9.8              #=> 0.22675736961451246

#<=>(numeric) ⇒ 1, ...

Performs comparison and returns -1, 0, or +1.

nil is returned if the two values are incomparable.

Rational(2, 3)  <=> Rational(2, 3)  #=> 0
Rational(5)     <=> 5               #=> 0
Rational(2,3)   <=> Rational(1,3)   #=> 1
Rational(1,3)   <=> 1               #=> -1
Rational(1,3)   <=> 0.3             #=> 1

#==(object) ⇒ Boolean

Returns true if rat equals object numerically.

Rational(2, 3)  == Rational(2, 3)   #=> true
Rational(5)     == 5                #=> true
Rational(0)     == 0.0              #=> true
Rational('1/3') == 0.33             #=> false
Rational('1/2') == '1/2'            #=> false

#abs ⇒ rat #magnitude ⇒ rat
Also known as: #magnitude

Returns the absolute value of rat.

(1/2r).abs    #=> 1/2r
(-1/2r).abs   #=> 1/2r

#magnitude is an alias of abs.

#ceil ⇒ Integer #ceil(precision = 0) ⇒ Rational

Returns the truncated value (toward positive infinity).

Rational(3).ceil      #=> 3
Rational(2, 3).ceil   #=> 1
Rational(-3, 2).ceil  #=> -1

  #    decimal      -  1  2  3 . 4  5  6
  #                   ^  ^  ^  ^   ^  ^
  #   precision      -3 -2 -1  0  +1 +2

'%f' % Rational('-123.456').ceil(+1)  #=> "-123.400000"
'%f' % Rational('-123.456').ceil(-1)  #=> "-120.000000"

#denominator ⇒ Integer

Returns the denominator (always positive).

Rational(7).denominator             #=> 1
Rational(7, 1).denominator          #=> 1
Rational(9, -4).denominator         #=> 4
Rational(-2, -10).denominator       #=> 5
rat.numerator.gcd(rat.denominator)  #=> 1

#fdiv(numeric) ⇒ Float

Performs division and returns the value as a float.

Rational(2, 3).fdiv(1)       #=> 0.6666666666666666
Rational(2, 3).fdiv(0.5)     #=> 1.3333333333333333
Rational(2).fdiv(3)          #=> 0.6666666666666666

#floor ⇒ Integer #floor(precision = 0) ⇒ Rational

Returns the truncated value (toward negative infinity).

Rational(3).floor      #=> 3
Rational(2, 3).floor   #=> 0
Rational(-3, 2).floor  #=> -1

  #    decimal      -  1  2  3 . 4  5  6
  #                   ^  ^  ^  ^   ^  ^
  #   precision      -3 -2 -1  0  +1 +2

'%f' % Rational('-123.456').floor(+1)  #=> "-123.500000"
'%f' % Rational('-123.456').floor(-1)  #=> "-130.000000"

#inspect ⇒ String

Returns the value as a string for inspection.

Rational(2).inspect      #=> "(2/1)"
Rational(-8, 6).inspect  #=> "(-4/3)"
Rational('1/2').inspect  #=> "(1/2)"

#abs ⇒ rat #magnitude ⇒ rat

Alias for #abs.

#numerator ⇒ Integer

Returns the numerator.

Rational(7).numerator        #=> 7
Rational(7, 1).numerator     #=> 7
Rational(9, -4).numerator    #=> -9
Rational(-2, -10).numerator  #=> 1

#/(numeric) ⇒ Numeric #quo(numeric) ⇒ Numeric

Alias for #/.

#rationalize ⇒ self #rationalize(eps) ⇒ Rational

Returns a simpler approximation of the value if the optional argument eps is given (rat-|eps| <= result <= rat+|eps|), self otherwise.

r = Rational(5033165, 16777216)
r.rationalize                    #=> (5033165/16777216)
r.rationalize(Rational('0.01'))  #=> (3/10)
r.rationalize(Rational('0.1'))   #=> (1/3)

#round ⇒ Integer #round(precision = 0) ⇒ Rational

Returns the truncated value (toward the nearest integer; 0.5 => 1; -0.5 => -1).

Rational(3).round      #=> 3
Rational(2, 3).round   #=> 1
Rational(-3, 2).round  #=> -2

  #    decimal      -  1  2  3 . 4  5  6
  #                   ^  ^  ^  ^   ^  ^
  #   precision      -3 -2 -1  0  +1 +2

'%f' % Rational('-123.456').round(+1)  #=> "-123.500000"
'%f' % Rational('-123.456').round(-1)  #=> "-120.000000"

#to_f ⇒ Float

Return the value as a float.

Rational(2).to_f      #=> 2.0
Rational(9, 4).to_f   #=> 2.25
Rational(-3, 4).to_f  #=> -0.75
Rational(20, 3).to_f  #=> 6.666666666666667

#to_i ⇒ Integer

Returns the truncated value as an integer.

Equivalent to #truncate.

Rational(2, 3).to_i   #=> 0
Rational(3).to_i      #=> 3
Rational(300.6).to_i  #=> 300
Rational(98,71).to_i  #=> 1
Rational(-30,2).to_i  #=> -15

#to_r ⇒ self

Returns self.

Rational(2).to_r      #=> (2/1)
Rational(-8, 6).to_r  #=> (-4/3)

#to_s ⇒ String

Returns the value as a string.

Rational(2).to_s      #=> "2/1"
Rational(-8, 6).to_s  #=> "-4/3"
Rational('1/2').to_s  #=> "1/2"

#truncate ⇒ Integer #truncate(precision = 0) ⇒ Rational

Returns the truncated value (toward zero).

Rational(3).truncate      #=> 3
Rational(2, 3).truncate   #=> 0
Rational(-3, 2).truncate  #=> -1

  #    decimal      -  1  2  3 . 4  5  6
  #                   ^  ^  ^  ^   ^  ^
  #   precision      -3 -2 -1  0  +1 +2

'%f' % Rational('-123.456').truncate(+1)  #=>  "-123.400000"
'%f' % Rational('-123.456').truncate(-1)  #=>  "-120.000000"